High glucose and diabetes modulate cellular proteasome function: Implications in the pathogenesis of diabetes complications

► Retinal endothelial cells exhibit higher proteasome peptidase activity compared to pericytes. ► High glucose treatment increased the levels of ubiquitinated proteins in retinal vascular cells. ► High glucose treatment enhanced the PA28 protein levels in pericytes but not endothelial cells. ► Diabetic retina and kidney have higher levels of PA28 proteasome regulatory proteins. ► The UPS components are increased within the glomerular capillaries of diabetic kidney.