Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part B

Author(s): Noriko Fujii, Takumi Takata, Norihiko Fujii, Kenzo Aki

Background Age-related cataracts, which probably form due to insolubilization of lens proteins, can lead to loss of vision. Although the exact reason is unknown, lens protein aggregation may be triggered by increases in PTMs such as d-β-, l-β- and d-α-Asp isomers. These isomers have been observed in aged lens; however, there have been few quantitative and site-specific studies owing to the lack of a quick and precise method for distinguishing between d- and l-Asp in a peptide or protein. Scope of review We describe a new method for detecting peptides containing Asp isomers at individual sites in any protein by using an LC–MS/MS system combined with commercial enzymes that specifically react with different isomers. We also summarize current data on the effect of Asp isomerization on lens crystallins. Major conclusions The new technique enabled the analysis of isomers of Asp residues in lens proteins precisely and quickly. An extensive proportion of Asp isomerization was observed at all Asp sites of crystallins in the insoluble fraction of aged lens. In addition, d-amino acid substitutions in crystallin-mimic peptides showed altered structural formation and function. These results indicate that isomerization of Asp residues affects the stability, structure and inter-subunit interaction of lens crystallins, which will induce crystallin aggregation and insolubilization, disrupt the associated functions, and ultimately contribute to the onset of senile cataract formation. General significance The mechanism underlying the onset of age-related diseases may involve isomerization, whereby d-amino acids are incorporated in the l-amino acid world of life. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
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Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part A

Author(s): Laura Pieri, Philippe Chafey, Morgane Le Gall, Guilhem Clary, Ronald Melki, Virginie Redeker


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Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part A

Author(s): Nicola Giangregorio, Annamaria Tonazzi, Lara Console, Imma Lorusso, Annalisa De Palma, Cesare Indiveri

Background The carnitine/acylcarnitine carrier (CAC or CACT) mediates transport of acylcarnitines into mitochondria for the β-oxidation. CAC possesses Cys residues which respond to redox changes undergoing to SH/disulfide interconversion. Methods The effect of H2S has been investigated on the [3H]carnitine/carnitine antiport catalyzed by recombinant or native CAC reconstituted in proteoliposomes. Site-directed mutagenesis was employed for identifying Cys reacting with H2S. Results H2S led to transport inhibition, which was dependent on concentration, pH and time of incubation. Best inhibition with IC50 of 0.70μM was observed at physiological pH after 30–60min incubation. At longer times of incubation, inhibition was reversed. After oxidation of the carrier by O2, transport activity was rescued by H2S indicating that the inhibition/activation depends on the initial redox state of the protein. The observed effects were more efficient on the native rat liver transporter than on the recombinant protein. Only the protein containing both C136 and C155 responded to the reagent as the WT. While reduced responses were observed in the mutants containing C136 or C155. Multi-alignment of known mitochondrial carriers, highlighted that only the CAC possesses both Cys residues. This correlates well with the absence of effects of H2S on carriers which does not contain the Cys couple. Conclusions Altogether, these data demonstrate that H2S regulates the CAC by inhibiting or activating transport on the basis of the redox state of the protein. General significance CAC represents a specific target of H2S among mitochondrial carriers in agreement with the presence of a reactive Cys couple.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part B

Author(s): Roger J.W. Truscott, Michael G. Friedrich

Background It is probable that the great majority of human cataract results from the spontaneous decomposition of long-lived macromolecules in the human lens. Breakdown/reaction of long-lived proteins is of primary importance and recent proteomic analysis has enabled the identification of the particular crystallins, and their exact sites of amino acid modification. Scope of review Analysis of proteins from cataractous lenses revealed that there are sites on some structural proteins that show a consistently greater degree of deterioration than age-matched normal lenses. Major conclusions The most abundant posttranslational modification of aged lens proteins is racemization. Deamidation, truncation and crosslinking, each arising from the spontaneous breakdown of susceptible amino acids within proteins, are also present. Fundamental to an understanding of nuclear cataract etiology, it is proposed that once a certain degree of modification at key sites occurs, that protein–protein interactions are disrupted and lens opacification ensues. General Significance Since long-lived proteins are now recognized to be present in many other sites of the body, such as the brain, the information gleaned from detailed analyses of degraded proteins from aged lenses will apply more widely to other age-related human diseases. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part A

Author(s): Paulo E. Cabral Filho, Ana L.C. Cardoso, Maria I.A. Pereira, Ana P.M. Ramos, Fernando Hallwass, M. Margarida C.A. Castro, Carlos F.G.C. Geraldes, Beate S. Santos, Maria C. Pedroso de Lima, Giovannia A.L. Pereira, Adriana Fontes

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part B

Author(s): Alok Kumar Panda, Sandip Kumar Nandi, Ayon Chakraborty, Ram H. Nagaraj, Ashis Biswas

Background α-Crystallin is a major protein of the eye lens in vertebrates. It is composed of two subunits, αA- and αB-crystallin. α-Crystallin is an oligomeric protein having these two subunits in 3:1 ratio. It belongs to small heat shock protein family and exhibits molecular chaperone function, which plays an important role in maintaining the lens transparency. Apart from chaperone function, both subunits also exhibit anti-apoptotic property. Comparison of their primary sequences reveals that αA- and αB-crystallin posses 13 and 14 arginine residues, respectively. Several of them undergo mutations which eventually lead to various eye diseases such as congenital cataract, juvenile cataract, and retinal degeneration. Interestingly, many arginine residues of these subunits are modified during glycation and even some are truncated during aging. All these facts indicate the importance of arginine residues in α-crystallin. Scope of review In this review, we will emphasize the recent in vitro and in vivo findings related to congenital cataract causing arginine mutations in α-crystallin. Major conclusions Congenital cataract causing arginine mutations alters the structure and decreases the chaperone function of α-crystallin. These mutations also affect the lens morphology and phenotypes. Interestingly, non-natural arginine mutations (generated for mimicking the glycation and truncation environment) improve the chaperone function of α-crystallin which may play an important role in maintaining the eye lens transparency during aging. General significance The neutralization of positive charge on the guanidino group of arginine residues is not always detrimental to the functionality of α-crystallin. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part A

Author(s): Sylvia Hiller, Robert DeKroon, Eric D. Hamlett, Longquan Xu, Cristina Osorio, Jennifer Robinette, Witold Winnik, Stephen Simington, Nobuyo Maeda, Oscar Alzate, Xianwen Yi

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part B

Author(s): A. Biswas, S. Karmakar, A. Chowdhury, K.P. Das

Background α-Crystallin acts like a molecular chaperone by interacting with its substrate proteins and thus prevents their aggregation. It also interacts with various kinds of small molecules that affect its structure and function. Scope of review In this article we will present a review of work done with respect to the interaction of ATP, peptide generated from lens crystallin and other proteins and some bivalent metal ions with α-crystallin and discuss the role of these interactions on its structure and function and cataract formation. We will also discuss the interaction of some hydrophobic fluorescence probes and surface active agents with α-crystallin. Major conclusions Small molecule interaction controls the structure and function of α-crystallin. ATP and Zn+2 stabilize its structure and enhance chaperone function. Therefore the depletion of these small molecules can be detrimental to maintenance of lens transparency. However, the accumulation of small peptides due to protease activity in the lens can also be harmful as the interaction of these peptides with α-crystallin and other crystallin proteins in the lens promotes aggregation and loss of lens transparency. The use of hydrophobic probe has led to a wealth of information regarding the location of substrate binding site and nature of chaperone–substrate interaction. Interaction of surface active agents with α-crystallin has helped us to understand the structural stability and oligomeric dissociation in α-crystallin. General significance These interactions are very helpful in understanding the mechanistic details of the structural changes and chaperone function of α-crystallin. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part A

Author(s): Christopher E. Jones, Meet Zandawala, Dean C. Semmens, Sarah Anderson, Graeme R. Hanson, Daniel A. Janies, Maurice R. Elphick

Background Neuropeptides with an Amino Terminal Cu(II), Ni(II) Binding (ATCUN) motif (H2N-xxH) bind Cu(II)/Ni(II) ions. Here we report the novel discovery of a neuropeptide precursor that gives rise to a “cocktail” of peptides that bind Cu(II)/Ni(II) and form ternary complexes — the L-type SALMFamide precursor in the starfish Asterias rubens. Methods Echinoderm transcriptome sequence data were analysed to identify transcripts encoding precursors of SALMFamide-type neuropeptides. The sequence of the L-type SALMFamide precursor in the starfish Asterias rubens was confirmed by cDNA sequencing and peptides derived from this precursor (e.g. AYHSALPF-NH2, GYHSGLPF-NH2 and LHSALPF-NH2) were synthesized. The ability of these peptides to bind metals was investigated using UV/Vis, NMR, circular dichroism and EPR spectroscopy. Results AYHSALPF-NH2 and GYHSGLPF-NH2 bind Cu(II) and Ni(II) and generate metal-linked dimers to form ternary complexes with LHSALPF-NH2. Investigation of the evolutionary history of the histidine residue that confers these properties revealed that it can be traced to the common ancestor of echinoderms, which is estimated to have lived ~500million years ago. However, L-type precursors comprising multiple SALMFamides with the histidine residue forming an ATCUN motif appears to be a feature that has evolved uniquely in starfish (Asteroidea). General Significance The discovery of a SALMFamide-type neuropeptide precursor protein that gives rise to a “cocktail” of peptides that bind metal ions and generate metal-linked dimers provides a new insight on ATCUN motif-containing neuropeptides. This property of L-type SALMFamides in the Asteroidea may be associated with a role in regulation of the unusual extra-oral feeding behaviour of starfish.
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Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part B

Author(s): Kumarasamy Anbarasu, Jeyarajan Sivakumar

Background Crystallins are the important structural and functional proteins in the eye lens responsible for refractive index. Post-translational modifications (PTMs) and mutations are major causative factors that affect crystallin structural conformation and functional characteristics thus playing a vital role in the etiology of cataractogenesis. Scope of review The significance of crystallin protein–protein interactions (PPIs) in the lens and non-lenticular tissues is summarized. Major conclusions Aberrancy of PPIs between crystallin, its associated protein and metal ions has been accomplished in various human diseases including cataract. A detailed account on multidimensional structural and functional significance of crystallin PPI in humans must be brought into limelight, in order to understand the biochemical and molecular basis augmenting the aberrancies of such interaction. In this scenario, the present review is focused to shed light on studies which will aid to expand our present understanding on disease pathogenesis related to loss of PPI thereby paving the way for putative future therapeutic targets to curb such diseases. General significance The interactions with α-crystallins always aid to protect their structural and functional characteristics. The up-regulation of αB-crystallin in the non-lenticular tissues always decodes as biomarker for various stress related disorders. For better understanding and treatment of various diseases, PPI studies provide overall outline about the structural and functional characteristics of the proteins. This information not only helps to find out the route of cataractogenesis but also aid to identify potential molecules to inhibit/prevent the further development of such complicated phenomenon. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part A

Author(s): Xiaofeng Yu, Prajwal Nandekar, Ghulam Mustafa, Vlad Cojocaru, Galina I. Lepesheva, Rebecca C. Wade

Background Cytochrome P450 sterol 14α-demethylase (CYP51) is an essential enzyme for sterol biosynthesis and a target for anti-parasitic drug design. However, the design of parasite-specific drugs that inhibit parasitic CYP51 without severe side effects remains challenging. The active site of CYP51 is situated in the interior of the protein. Here, we characterize the potential ligand egress routes and mechanisms in Trypanosoma brucei and human CYP51 enzymes. Methods We performed Random Acceleration Molecular Dynamics simulations of the egress of four different ligands from the active site of models of soluble and membrane-bound T. brucei CYP51 and of soluble human CYP51. Results In the simulations, tunnel 2f, which leads to the membrane, was found to be the predominant ligand egress tunnel for all the ligands studied. Tunnels S, 1 and W, which lead to the cytosol, were also used in T. brucei CYP51, whereas tunnel 1 was the only other tunnel used significantly in human CYP51. The common tunnels found previously in other CYPs were barely used. The ligand egress times were shorter for human than T. brucei CYP51, suggesting lower barriers to ligand passage. Two gating residues, F105 and M460, in T. brucei CYP51 that modulate the opening of tunnels 2f and S were identified. Conclusions Although the main egress tunnel was the same, differences in the tunnel-lining residues, ligand passage and tunnel usage were found between T. brucei and human CYP51s. General Significance The results provide a basis for the design of selective anti-parasitic agents targeting the ligand tunnels.
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Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part B

Author(s): Usha P. Andley, Joshua W. Goldman

Background Knock-in mice provide useful models of congenital and age-related cataracts caused by α-crystallin mutations. R49C αA-crystallin and R120G αB-crystallin mutations are linked with hereditary cataracts. Knock-in αA-R49C+/− heterozygotes develop cataracts by 1–2months, whereas homozygote mice have cataracts at birth. The R49C mutation drastically reduces lens protein water solubility and causes cell death in knock-in mouse lenses. Mutant crystallin cannot function as a chaperone, which leads to protein aggregation and lens opacity. Protein aggregation disrupts the lens fiber cell structure and normal development and causes cell death in epithelial and fiber cells. We determined what aspects of the wild-type phenotype are age-dependently altered in the mutant lens. Methods Wild-type, heterozygote (αA-R49C+/−), and homozygote (αA-R49C+/+) mouse lenses were assessed pre- and postnatally for lens morphology (electron microscopy, immunohistochemistry), and autophagy or unfolded protein response markers (immunoblotting). Results Morphology was altered by embryonic day 17 in R49C+/+ lenses; R49C+/− lens morphology was unaffected at this stage. Active autophagy in the lens epithelium of mutant lenses was indicated by the presence of autophagosomes using electron microscopy. Protein p62 levels, which are degraded specifically by autophagy, increased in αA-R49C mutant versus wild-type lenses, suggesting autophagy inhibition in the mutant lenses. The unfolded protein response marker XBP-1 was upregulated in adult lenses of αB-R120G+/+ mice, suggesting its role in lens opacification. Conclusions Mutated crystallins alter lens morphology, autophagy, and stress responses. General significance Therapeutic modulation of autophagic pathways may improve protein degradation in cataractous lenses and reduce lens opacity. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part A

Author(s): Marta Bou, Marijana Todorčević, Jacob Torgersen, Stanko Škugor, Isabel Navarro, Bente Ruyter

Background Carnivorous teleost fish utilize glucose poorly, and the reason for this is not known. It is possible that the capacity of adipocytes to synthesize lipids from carbohydrate precursors through a process known as “de novo lipogenesis” (DNL) is one of the factors that contributes to glucose intolerance in Atlantic salmon. Methods Primary adipocytes from Atlantic salmon differentiated in vitro were incubated with radiolabelled glucose in order to explore the capacity of salmon adipocytes to synthesize and deposit lipids from glucose through DNL. The lipid-storage capacity of adipocytes incubated with glucose was compared with that of cells incubated with the fatty acid palmitic acid. Quantitative PCR and immunohistochemistry were used to assess changes of genes and proteins involved in glucose and lipid transport and metabolism. Results Less than 0.1% of the radiolabelled glucose was metabolized to the fatty acids 16:0 and the stearoyl-CoA desaturase products 16:1 and 18:1 by DNL, whereas approximately 40% was converted to glycerol to form the triacylglycerol backbone of lipids. Transcriptional analysis indicated that adipocytes ensure the availability of necessary cofactors and other substrates for lipid synthesis and storage from glycolysis, the pentose phosphate pathway and glyceroneogenesis. Conclusions We have shown for the first time that the DNL pathway is active in fish adipocytes. The capacity of the pathway to convert glucose into cellular lipids for storage is relatively low. General significance The limited capacity of adipocytes to utilize glucose as a substrate for lipid deposition may contribute to glucose intolerance in salmonids.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part B

Author(s): John I. Clark

Background Human alphaB crystallin (HspB5) contains the alpha crystallin core domain, a series of antiparallel beta-strands organized into the characteristic beta sandwich of small heat shock proteins (sHsps). The full 3-dimensional structure for alpha crystallin has not been determined and the mechanism for the biological activity remains elusive because sHsps participate in multiple interactions with a broad range of target proteins that favor self-assembly of polydisperse fibrils and complexes. We selected human alphaB crystallin to study interactive sequences because it is involved in many human condensation, amyloid, and aggregation diseases and it is very sensitive to the destabilization of unfolding proteins. Sophisticated methods are being used to analyze and complete the structure of alphaB crystallin with the expectation of understanding sHsp function. This review considers the identification of interactive sites on the surface of the alphaB crystallin, which may be the key to understanding the multifunctional activity of human alphaB crystallin. Scope of review This review summarizes the research on the identification of the bioactive interactive sequences responsible for the function of human alphaB crystallin, an sHsp with chaperone-like activity. Major conclusions The multifunctional activity of human alphaB crystallin results from the interactive peptide sequences exposed on the surface of the molecule. The multiple, non-covalent, interactive sequences can account for the selectivity and sensitivity of alphaB crystallin to the initiation of protein unfolding. General significance Human alphaB crystallin may be an important part of an endogenous protective mechanism in aging cells and tissues. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part A

Author(s): Itzhel García-Torres, Ignacio de la Mora-de la Mora, Jaime Marcial-Quino, Saúl Gómez-Manzo, América Vanoye-Carlo, Gabriel Navarrete-Vázquez, Blanca Colín-Lozano, Pedro Gutiérrez-Castrellón, Edgar Sierra-Palacios, Gabriel López-Velázquez, Sergio Enríquez-Flores

Background Proton pump inhibitors (PPIs) are extensively used in clinical practice because of their effectiveness and safety. Omeprazole is one of the best-selling drugs worldwide and, with other PPIs, has been proposed to be potential drugs for the treatment of several diseases. We demonstrated that omeprazole shows cytotoxic effects in Giardia and concomitantly inactivates giardial triosephosphate isomerase (GlTIM). Therefore, we evaluated the efficiency of commercially available PPIs to inactivate this enzyme. Methods We assayed the effect of PPIs on the GlTIM WT, single Cys mutants, and the human counterpart, following enzyme activity, thermal stability, exposure of hydrophobic regions, and susceptibility to limited proteolysis. Results PPIs efficiently inactivated GlTIM; however, rabeprazole was the best inactivating drug and was nearly ten times more effective. The mechanism of inactivation by PPIs was through the modification of the Cys 222 residue. Moreover, there are important changes at the structural level, the thermal stability of inactivated-GlTIM was drastically diminished and the structural rigidity was lost, as observed by the exposure of hydrophobic regions and their susceptibility to limited proteolysis. Conclusions Our results demonstrate that rabeprazole is the most potent PPI for GlTIM inactivation and that all PPIs tested have substantial abilities to alter GITIM at the structural level, causing serious damage. General significance. This is the first report demonstrating the effectiveness of commercial PPIs on a glycolytic parasitic enzyme, with structural features well known. This study is a step forward in the use and understanding the implicated mechanisms of new antigiardiasic drugs safe in humans.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part B

Author(s): Murugesan Raju, Puttur Santhoshkumar, K. Krishna Sharma

Background The demonstration of chaperone-like activity in peptides (mini-chaperones) derived from α-crystallin's chaperone region has generated significant interest in exploring the therapeutic potential of peptide chaperones in diseases of protein aggregation. Recent studies in experimental animals show that mini-chaperones could reach intended targets and alter the disease phenotype. Although mini-chaperones show potential benefits against protein aggregation diseases, they do tend to form aggregates on storage. There is thus a need to fine-tune peptide chaperones to increase their solubility, pharmacokinetics, and biological efficacy. Scope of review This review summarizes the properties and the potential therapeutic roles of mini-chaperones in protein aggregation diseases and highlights some of the refinements needed to increase the stability and biological efficacy of mini-chaperones while maintaining or enhancing their chaperone-like activity against precipitation of unfolding proteins. Major conclusions Mini-chaperones suppress the aggregation of proteins, block amyloid fibril formation, stabilize mutant proteins, sequester metal ions, and exhibit antiapoptotic properties. Much work must be done to fine-tune mini-chaperones and increase their stability and biological efficacy. Peptide chaperones could have a great therapeutic value in diseases associated with protein aggregation and apoptosis. General significance Accumulation of misfolded proteins is a primary cause for many age-related diseases, including cataract, macular degeneration, and various neurological diseases. Stabilization of native proteins is a logical therapeutic approach for such diseases. Mini-chaperones, with their inherent antiaggregation and antiapoptotic properties, may represent an effective therapeutic molecule to prevent the cascade of protein conformational disorders. Future studies will further uncover the therapeutic potential of mini-chaperones. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part A

Author(s): Y. Schilt, T. Berman, X. Wei, Y. Barenholz, U. Raviv

Background Among nanodrugs, PEGylated nanoliposomes loaded with an active agent are of major importance. In this paper we studied the structures and morphology of PEGylated nanoliposomes before and after remote loading with doxorubicin. Methods High-resolution structures were obtained by solution X-ray scattering combined with our advanced analysis tools. We studied the PEGylated liposomal doxorubicin (PLD) product Doxil®, and its generics, where remote doxorubicin loading is performed by a gradient of ammonium sulfate, and LC100, a novel PLD under development, where remote loading was done by a gradient of ammonium methanesulfonate. The PLD structures were compared with drug-free nanoliposomes having identical composition. Results We determined the membrane electron density profiles of the empty and loaded PLDs, the thickness and density of the PEG layers, and the structure of the drug inside the liposomes. Conclusions The liposomal membranes had the same structure for both ammonium salts. We found that the drug formed crystals inside PLDs loaded by ammonium sulfate, whereas it had an amorphous morphology in the PLD loaded by ammonium methanesulfonate. The variations of the drug's structural parameters between the generics of Doxil® are similar to the variations between batches of the same product, suggesting that all these products were structurally similar. General significance This paper demonstrates that solution X-ray scattering, when combined with our powerful analysis tools, can determine the high-resolution structure of complex non-crystallized nanoparticle dispersions used in nanomedicine, thereby providing useful physical insights into their functions.
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Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part B

Author(s): Ram H. Nagaraj, Rooban B. Nahomi, Niklaus H. Mueller, Cibin T. Raghavan, David A. Ammar, J. Mark Petrash

Background The findings that α-crystallins are multi-functional proteins with diverse biological functions have generated considerable interest in understanding their role in health and disease. Recent studies have shown that chaperone peptides of α-crystallin could be delivered into cultured cells and in experimental animals with beneficial effects against protein aggregation, oxidation, inflammation and apoptosis. Scope of review In this review, we will summarize the latest developments on the therapeutic potential of α-crystallins and their functional peptides. Major conclusions α-Crystallins and their functional peptides have shown significant favorable effects against several diseases. Their targeted delivery to tissues would be of great therapeutic benefit. However, α-crystallins can also function as disease-causing proteins. These seemingly contradictory functions must be carefully considered prior to their therapeutic use. General significance αA and αB-Crystallin are members of the small heat shock protein family. These proteins exhibit molecular chaperone and anti-apoptotic activities. The core crystallin domain within these proteins is largely responsible for these prosperities. Recent studies have identified peptides within the crystallin domain of both α- and αB-crystallins with remarkable chaperone and anti-apoptotic activities. Administration of α-crystallin or their functional peptides has shown substantial inhibition of pathologies in several diseases. However, α-crystallins have been shown to promote disease-causing pathways. These two sides of the proteins are discussed in this review. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part A

Author(s): Fuzhou Tang, Yang Ren, Ruofeng Wang, Xiaofeng Lei, Xueru Deng, Yajin Zhao, Dong Chen, Xiang Wang

Background In physiological and pathological conditions activated protein kinace C (PKC) has been observed in the erythrocytes. Externalization of ankyrin followed by Arg–Gly–Asp (RGD)/integrin recognition also triggers erythrophagocytosis. In the present study, to test whether activated PKC is associated with ankyrin exposure in erythrophagocytosis. Methods Phorbol 12-myristate-13-acetate (PMA)-induced PKC activation and ankyrin phosphorylation were tested, and under different treatment conditions the subpopulation of erythrocytes with ankyrin exposure and the levels of intracellular calcium were analyzed by flow cytometry. Results Results showed that treatment of erythrocytes with PMA in a calcium-containing buffer led to ankyrin exposure. In the absence of extracellular calcium, no ankyrin exposure was observed. PKC inhibition with calphostin C, a blocker of the PMA binding site, completely prevented the calcium entry, protein phosphorylation and ankyrin exposure. PKC inhibition with chelerythrine chloride, an inhibitor of the active site, diminished the level of ankyrin-exposing cells and ankyrin phosphorylation; however it even led to a higher percentage of cells with increased levels of calcium than with PMA treatment alone. Although PKC was activated and ankyrin phosphorylation occurred, no ankyrin exposure was observed in the absence of extracellular calcium. Conclusion Analyses of results suggested that PMA induces calcium influx into the erythrocytes, leading to the activation of calcium-dependent enzymes and the phosphorylation of membrane proteins, ultimately inducing ankyrin exposure and erythrophagocytosis. This study may provide insights into the molecular mechanisms of removing aged or diseased erythrocytes.

Publication date: January 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects, Volume 1860, Issue 1, Part B

Author(s): Ram Kannan, Parameswaran G. Sreekumar, David R. Hinton

Background αA- and αB crystallins are principal members of the small heat shock protein family and elicit both a cell protective function and a chaperone function. α-Crystallins have been found to be prominent proteins in normal and pathological retina emphasizing the importance for in-depth understanding of their function and significance. Scope of review Retinal pigment epithelial cells (RPE) play a vital role in the pathogenesis of age-related macular degeneration (AMD). This review addresses a number of cellular functions mediated by α-crystallins in the retina. Prominent expression of αB crystallin in mitochondria may serve to protect cells from oxidative injury. αB crystallin as secretory protein via exosomes can offer neuroprotection to adjacent RPE cells and photoreceptors. The availability of chaperone-containing minipeptides of αB crystallin could prove to be a valuable new tool for therapeutic treatment of retinal disorders. Major conclusions α-Crystallins are expressed in cytosol and mitochondria of RPE cells and are regulated during oxygen-induced retinopathy and during development. α-Crystallins protect RPE from oxidative-and ER stress-induced injury and autophagy. αB-Crystallin is a modulator of angiogenesis and vascular endothelial growth factor. αB Crystallin is secreted via exosomal pathway. Minichaperone peptides derived from αB Crystallin prevent oxidant induced cell death and have therapeutic potential. General significance Overall, this review summarizes several novel properties of α-crystallins and their relevance to maintaining normal retinal function. In particular, the use of α-crystallin derived peptides is a promising therapeutic strategy to combat retinal diseases such as AMD. This article is part of a Special Issue entitled Crystallin biochemistry in health and disease.