hsp70 genes in the human genome: Conservation and differentiation patterns predict a wide array of overlapping and specialized functions

<p>Abstract</p> <p>Background</p> <p>Hsp70 chaperones are required for key cellular processes and response to environmental changes and survival but they have not been fully characterized yet. The human <it>hsp70</it>-gene family has an unknown number of members (eleven counted over ten years ago); some have been described but the information is incomplete and inconsistent. A coherent body of knowledge encompassing all family components that would facilitate their study individually and as a group is lacking. Nowadays, the study of chaperone genes benefits from the availability of genome sequences and a new protocol, chaperonomics, which we applied to elucidate the human <it>hsp70 </it>family.</p> <p>Results</p> <p>We identified 47 hsp70 sequences, 17 genes and 30 pseudogenes. The genes distributed into seven evolutionarily distinct groups with distinguishable subgroups according to phylogenetic and other data, such as exon-intron and protein features. The N-terminal ATP-binding domain (ABD) was conserved at least partially in the majority of the proteins but the C-terminal substrate-binding domain (SBD) was not. Nine proteins were typical Hsp70s (65–80 kDa) with ABD and SBD, two were lighter lacking partly or totally the SBD, and six were heavier (>80 kDa) with divergent C-terminal domains. We also analyzed exon-intron features, transcriptional variants and protein structure and isoforms, and modality and patterns of expression in various tissues and developmental stages. Evolutionary analyses, including human <it>hsp70 </it>genes and pseudogenes, and other eukaryotic <it>hsp70 </it>genes, showed that six human genes encoding cytosolic Hsp70s and 27 pseudogenes originated from retro-transposition of HSPA8, a gene highly expressed in most tissues and developmental stages.</p> <p>Conclusion</p> <p>The human <it>hsp70</it>-gene family is characterized by a remarkable evolutionary diversity that mainly resulted from multiple duplications and retrotranspositions of a highly expressed gene, HSPA8. Human Hsp70 proteins are clustered into seven evolutionary Groups, with divergent C-terminal domains likely defining their distinctive functions. These functions may also be further defined by the observed differences in the N-terminal domain.</p

Chaperonin genes on the rise: new divergent classes and intense duplication in human and other vertebrate genomes

<p>Abstract</p> <p>Background</p> <p>Chaperonin proteins are well known for the critical role they play in protein folding and in disease. However, the recent identification of three diverged chaperonin paralogs associated with the human Bardet-Biedl and McKusick-Kaufman Syndromes (BBS and MKKS, respectively) indicates that the eukaryotic chaperonin-gene family is larger and more differentiated than previously thought. The availability of complete genome sequences makes possible a definitive characterization of the complete set of chaperonin sequences in human and other species.</p> <p>Results</p> <p>We identified fifty-four chaperonin-like sequences in the human genome and similar numbers in the genomes of the model organisms mouse and rat. In mammal genomes we identified, besides the well-known CCT chaperonin genes and the three genes associated with the MKKS and BBS pathological conditions, a newly-defined class of chaperonin genes named CCT8L, represented in human by the two sequences CCT8L1 and CCT8L2. Comparative analyses from several vertebrate genomes established the monophyletic origin of chaperonin-like MKKS and BBS genes from the CCT8 lineage. The CCT8L gene originated from a later duplication also in the CCT8 lineage at the onset of mammal evolution and duplicated in primate genomes. The functionality of CCT8L genes in different species was confirmed by evolutionary analyses and in human by expression data. Detailed sequence analysis and structural predictions of MKKS, BBS and CCT8L proteins strongly suggested that they conserve a typical chaperonin-like core structure but that they are unlikely to form a CCT-like oligomeric complex. The characterization of many newly-discovered chaperonin pseudogenes uncovered the intense duplication activity of eukaryotic chaperonin genes.</p> <p>Conclusions</p> <p>In vertebrates, chaperonin genes, driven by intense duplication processes, have diversified into multiple classes and functionalities that extend beyond their well-known protein-folding role as part of the typical oligomeric chaperonin complex, emphasizing previous observations on the involvement of individual CCT monomers in microtubule elongation. The functional characterization of newly identified chaperonin genes will be a challenge for future experimental analyses.</p

HSPD1 (Heat Shock 60kDa Protein 1)

The HSPD1 gene encodes a protein known as HSP60 or Hsp60, also commonly referred to as Cpn60. This protein is a molecular chaperone typically localized inside mitochondria where it forms a chaperoning machine with HSP10 (encoded by the HSPE1 gene), also called Cpn10, to assist protein folding inside the organelle. Hsp60 also occurs in the cytosol, plasma-cell membrane, intercellular space, and blood. Its functions in all these extramitochondrial locations are poorly understood. While the canonical functions of Hsp60 are considered to be cytoprotective, anti-stress and maintenance of protein homeostasis, other roles are currently being investigated. For example, Hsp60 participates in the pathogenesis of diseases in various ways in certain types of cancer, and chronic inflammatory and autoimmune pathological conditions. These are considered chaperonopathies by mistake, in which a normal chaperone (normal at least as far as it can be determined by current methods to study the structure of a molecule available only at extremely low concentrations and quantities) turns against the organism instead of protecting it, favouring the growth and dissemination of cancer cells, or the initiation-progression of inflammation, for instance. In addition, Hsp60 mutations cause at least two types of severe genetic chaperonopathies. All this knowledge is expanding nowadays clearly pointing to Hsp60 as a potential target for chaperonotherapy by replacement when it is defective or by inhibition when it is pathogenic

The molecular anatomy of human Hsp60 and its effects on Amyloid-β peptide

Heat Shock Protein 60 (HSP60) is ubiquitous and highly conserved, being present in eukaryotes and prokaryotes, including pathogens. This chaperonin is typically considered a mitochondrial protein but it is also found in other intracellular sites, extracellularly and in circulation. HSP60 is an indispensable component of the Chaperoning System and plays a key role in protein quality control, preventing off-pathway folding events and refolding misfolded proteins. This makes HSP60 a putative therapeutic agent for neurodegenerative diseases associated with aggregation of misfolded proteins, for example, Alzheimer’s Disease. We produced and purified recombinant human HSP60 and investigated the effects of its monomeric and tetradecameric forms onAmyloid-β aggregation. In addition, we induced oligomerization of HSP60 monomers by means of ATP. We measuredHSP60 stability in relation to degree of oligomerization. The structural stability of the HSP60 forms were also investigated by differential scanning calorimetry and isothermal titration calorimetry. The protein purified mainly appears in multimeric forms with a large fraction in dimers and monomers. We observed that Hsp60 is less stable in its monomeric form, but is more active in inhibiting the fibrillogenesis of beta amyloid peptide

Hsp60 Response in Experimental and Human Temporal Lobe Epilepsy due to hyppocampal sclerosis

Hsp60 is widely distributed in the brain, and its alteration has been involved in different neurological disorders. Epilepsy is considered one of the most common neurological disorders and typically involves the hippocampal formation. Compelling evidence describes a role of mitochondria, oxidative stress and both innate and adaptive immunity during epileptogenesis in temporal lobe epilepsy due to hyppocampal sclerosis (TLE-HS). Here, we investigate the Hsp60 involvement in experimental and human epilepsy. Firstly, expression and distribution of Hsp60 in epileptic hippocampi of a rat model of temporal lobe epilepsy (TLE), based on the phenomenon of maximal dentate gyrus activation (MDA), using western blotting and immunohistochemistry was evaluated. Moreover, the circulating levels of Hsp60 in the plasma derived from the blood of TLE-HS patients before and after epileptic seizure and agematched controls, using ELISA were investigated. Protein level and immunostaining of Hsp60 were increased in both the ipsilateral and contralateral hippocampi of the epileptic rats. The Hsp60 up-regulation was observed on neurons somata and neuropil of the dentate gyrus (DG) and in hippocampus proper (CA3, CA1). Moreover, Hsp60 plasmatic levels in patients after epilepitic seizure, compared to levels of the same subjects before seizure was significantly higher. These results demonstrate that Hsp60 synthesis is increased in response to epileptic seizures and could be used as a biomarker for hippocampal stress response in TLE-HS. In conclusion, our findings suggest that Hsp60 could play an importanty role in TLE-HS and support the possible involvement of immunological factors in epileptogenesis

Genes in the human genome: Conservation and differentiation patterns predict a wide array of overlapping and specialized functions-4

D for Figure 3 and text for methods and other details. Homologs of human HSPA12A and HSPA12B were found only in vertebrates. The evolutionary tree suggests that the human genes originated from a unique progenitor also appearing in fish possibly due to a duplication event that occurred in Tetrapoda before the divergence of Amphibia. Only one HSPA12 copy was found in reptiles and birds, suggesting gene loss (or extreme divergence) of one HSPA12 copy from this lineage.<p><b>Copyright information:</b></p><p>Taken from "genes in the human genome: Conservation and differentiation patterns predict a wide array of overlapping and specialized functions"</p><p>http://www.biomedcentral.com/1471-2148/8/19</p><p>BMC Evolutionary Biology 2008;8():19-19.</p><p>Published online 23 Jan 2008</p><p>PMCID:PMC2266713.</p><p></p

Genes in the human genome: Conservation and differentiation patterns predict a wide array of overlapping and specialized functions-1

Genes with the gene from which they originated, indicated by an asterisk. A similar tree (not shown) was obtained using the maximum-likelihood approach implemented in the program PHYML [40]. See legend for Figure 1 and text for details on Methods.<p><b>Copyright information:</b></p><p>Taken from "genes in the human genome: Conservation and differentiation patterns predict a wide array of overlapping and specialized functions"</p><p>http://www.biomedcentral.com/1471-2148/8/19</p><p>BMC Evolutionary Biology 2008;8():19-19.</p><p>Published online 23 Jan 2008</p><p>PMCID:PMC2266713.</p><p></p