C-terminal Hsp90 inhibitors also prevent A2535-induced neurotoxicity in SH-SY5Y neuroblastoma cells [32,33]. still develop and represent a significant risk to the overall deterioration of the health of the individual. DPN is the overall attrition of sensory nerve fibers that results from diabetes. Treatments for DPN generally offer monosymptomatic relief (e.g. analgesics to mitigate painful neuropathy) or specifically inhibit single, putative pathogenic mechanisms associated with diabetes-induced hyperglycemia [e.g. antioxidants, aldose reductase inhibitors, and poly(ADP-ribose) polymerase (PARP) inhibitors] [1,2]. Mismanaged insulin therapy can also generate symptoms of insulin shock (acute hyperinsulinism), depriving the brain of essential glucose, or diabetic encephalopathy (hypoinsulinism) [3]. For this reason, treatment of DPN can benefit from a more multifaceted therapeutic approach. In addition to managing non-neuronal postprandial glucose uptake, insulin and IGF signaling are required during early neurological development and to maintain neuronal viability and function throughout the nervous system [47]. Several components of insulin and Mouse monoclonal to GATA1 insulin-like growth factor-I (IGF-I) signaling, including insulin receptors (commonly mutated in insulin-resistant patients) Yoda 1 and IGF-I receptors, rely upon heat shock proteins (Hsps) for post-translational modifications and integrity [811]. Here we review Hsps and their role within normal and pathological insulin/IGF systems with an emphasis upon their potential as therapeutic targets. == The heat shock response == Several Hsps serve as molecular Yoda 1 chaperones that assist in the folding of nascent polypeptides, or client proteins, into their mature conformations [1215]. These chaperones also assist in the refolding of damaged proteins that arise under stressed conditions, such as nutrient deprivation, oxidative and nitrosative stress, and assorted insults to the cell [1215]. Additionally, Hsps serve as intracellular triage units that refold damaged proteins, tag irreparable proteins for proteolytic degradation, stabilize protein complexes, solubilize protein aggregates and facilitate intracellular trafficking [1216]. == Heat shock protein 90 (Hsp90) and heat shock factor 1 (HSF1) == Hsp90 is a 90 kDa homodimeric cytosolic protein that interacts with more than 200 client proteins and ~50 co-chaperones [1215,17]. Although all the molecular details by which Hsp90 folds client proteins remain unresolved, the molecular components of the folding machinery have been well-studied. The co-chaperones Hsp70 and Hsp40 Yoda 1 bind polypeptide substrates and are recruited into a heteroprotein complex with Hsp90 and Hsp70/Hsp90-organizing protein (HOP) [17]. This stabilized complex enables client protein transfer to the Hsp90 homodimer, thereby permitting Hsp70, Hsp40 and HOP dissociation in some cases [17]. Additional co-chaperones and immunophilins aid ATP binding within the Hsp90 N-terminal nucleotide-binding domain, promoting N-termini dimerization and clamping of the client protein [17]. Co-chaperone p23 further stabilizes the clamped protein complex and modulates nucleotide hydrolysis by altering the intrinsic ATPase activity of Hsp90 [17]. ATPase homolog 1 (AHA1) then initiates ATP hydrolysis to produce the energy necessary to induce conformational changes essential to client protein folding and release [17]. N-terminal Hsp90 inhibitors function by blocking ATP-mediated dimerization Yoda 1 and clamping of the client protein, destabilizing the complex and prematurely releasing the client protein [18]. Failure to produce mature client proteins is typically cytotoxic because cellular levels can decrease following ubiquitination, and proteasomal degradation of improperly folded proteins [17,18]. Chaperones are also essential for the refolding of aggregated, damaged and denatured proteins. Under normal conditions, Hsp90 binds HSF1, and this complex prevents the HSR [19,20]. Upon stress or heat shock, Hsp90 Yoda 1 releases HSF1 and ultimately induces the HSR following phosphorylation,.