Divergence of intracellular and extracellular HSP72 in type 2 diabetes: does fat matter?

Mammalian cells have developed a range of adaptations to survive against acute and prolonged (but not lethal) stresses (Beckmann et al. 1992). Among these adaptations, the heat shock response is the most conserved, being found in all prokaryotes and eukaryotes (Locke and Noble 1995). Heat shock proteins (HSPs) are considered part of a family of proteins known as "stress proteins" since their expression is induced by a wide range of stressors, such as oxidative stress (Krause et al. 2007), thermal stress (Yang et al. 1996), ischaemia (Richard et al. 1996), exercise (Krause et al. 2007), metabolic stress (Beckmann et al. 1992) and many others. The genes encoding Hsps are highly conserved, and many of these genes and their protein products can be assigned to different families on the basis of their typical molecular weight (kDa): HSP110 (or officially named HSPH), HSP90 (or HSPC), HSP70 (or HSPA), HSP60 (or HSPD1), HSP40 (or DNAJ) and small hsp families (HSPB) (Kampinga et al. 2009). In eukaryotes, many families comprise multiple members that differ in inducibility, intracellular localization and function (Feder and Hofmann 1999).