Modulation of α2C adrenergic receptor temperature-sensitive trafficking by HSP90

Decreasing the temperature to 30 C is accompanied by significant enhancement of alpha(2C)-AR plasma membrane levels in several cell lines with fibroblast phenotype, as demonstrated by radioligand binding in intact cells. No changes were observed on the effects of low-temperature after blocking receptor internalization in alpha(2C)-AR transfected HEK293T cells. In contrast, two pharmacological chaperones, dimethyl sulfoxide and glycerol, increased the cell surface receptor levels at 37 degrees C, but not at 30 degrees C. Further, at 37 degrees C alpha(2C)-AR is co-localized with endoplasmic reticulum markers, but not with the lysosomal markers. Treatment with three distinct HSP90 inhibitors, radicicol, macbecin and 17-DMAG significantly enhanced alpha(2C)-AR cell surface levels at 37 degrees C, but these inhibitors had no effect at 30 degrees C. Similar results were obtained after decreasing the HSP90 cellular levels using specific siRNA. Co-immunoprecipitation experiments demonstrated that alpha(2C)-AR interacts with HSP90 and this interaction is decreased at 30 degrees C. The contractile response to endogenous alpha(2C)-AR stimulation in rat tail artery was also enhanced at reduced temperature. Similar to HEK293T cells, HSP90 inhibition increased the alpha(2C)-AR contractile effects only at 37 degrees C. Moreover, exposure to low-temperature of vascular smooth muscle cells from rat tail artery decreased the cellular levels of HSP90, but did not change HSP70 levels. These data demonstrate that exposure to low-temperature augments the alpha(2C)-AR transport to the plasma membrane by releasing the inhibitory activity of HSP90 on the receptor traffic, findings which may have clinical relevance for the diagnostic and treatment of Raynaud Phenomenon. (C) 2010 Elsevier B.V. All rights reserved.