Heat Shock Proteins and Its Regulation
Heat stress leads to severe cellular damage resulting in production of cellular toxins and impaired protein synthesis. During such a stressful situation, the heat shock proteins (HSPs) play a vital role to maintain cellular homeostasis and thus are the ideal biomarker for heat stress.
This group of proteins are well known as the ‘molecular chaperones’ for their vital cytoprotective functions like folding of proteins in various intracellular compartments, maintenance of structural proteins, refolding of misfolded proteins, translocation of proteins across membranes and into various cellular compartments, prevention of protein aggregation and degradation of unstable proteins. HSPs also regulate the apoptotic signalling pathways where HSP27, HSP70 and HSP90 proteins are predominantly antiapoptotic, and HSP60 is proapoptotic. The principal HSPs that have chaperonic activity belong to five conserved classes, HSP33, HSP60, HSP70, HSP90, HSP100 and the small HSPs. Heat shock factors (HSFs) present in the cytosol are attached with HSPs and maintained in an inactive state. Heat stress or stressors activate HSFs and detach from HSPs, and phosphorylation of HSFs by protein kinases leads to formation of trimers in the cytosol. These HSF trimer complexes enter into the nucleus and bind with heat shock elements (HSE) in the promoter region of the HSP genes. HSP mRNA is transcribed and exits the nucleus to enter in the cytosol, where new HSPs are synthesized. The primary activity of HSPs is to sustain translation and protein integrity in the cells. Cells that become thermo-tolerant also produced less HSP during a second challenge compared to the previous heat stress exposure, suggesting HSP synthesis is also regulated depending on the levels of these proteins within the cell. HSPs are highly important in all the organisms which protect the cells against varied stressful circumstances and critically essential for normal cellular function.28.6
More on the topic Heat Shock Proteins and Its Regulation:
-
Veterinarian -