Agonist-induced Down-regulation of Endogenous Protein Kinase C α through an Endolysosomal Mechanism
Year: 2013
Type: article
Abstract: Background: Mechanisms of endogenous PKC signal termination remain to be fully characterized.Results: Activated endogenous PKC␣ undergoes dynamin-dependent and -independent endocytic uptake and traffics through early and late endosomes for processing by lysosomes.Conclusion: Lysosomal degradation represents a novel mechanism of desensitizing PKC-mediated signaling.Significance: Multiple degradation mechanisms ensure strict control of the duration of PKC signaling in cells. Protein kinase C (PKC) isozymes undergo down-regulation upon sustained stimulation. Previous studies have pointed to the existence of both proteasome-dependent and -independent pathways of PKC␣ processing.Here we demonstrate that these down-regulation pathways are engaged in different subcellular compartments; proteasomal degradation occurs mainly at the plasma membrane, whereas non-proteasomal processing occurs in the perinuclear region.Using cholesterol depletion, pharmacological inhibitors, RNA interference, and dominant-negative mutants, we define the mechanisms involved in perinuclear accumulation of PKC␣ and identify the non-proteasomal mechanism mediating its degradation.We show that intracellular accumulation of PKC␣ involves at least two clathrin-independent, cholesterol/lipid raft-mediated pathways that do not require ubiquitination of the protein; one is dynamin-dependent and likely involves caveolae, whereas the other is dynaminand small GTPase-independent.Internalized PKC␣ traffics through endosomes and is delivered to the lysosome for degradation.Supportive evidence includes (a) detection of the enzyme in EEA1-positive early endosomes, Rab7-positive late endosomes/multivesicular bodies, and LAMP1-positive lysosomes and (b) inhibition of its down-regulation by lysosomedisrupting agents and leupeptin.Only limited dephosphorylation of PKC␣ occurs during trafficking, with fully mature enzyme being the main target for lysosomal degradation.These studies define a novel and widespread mechanism of desensitization of PKC␣ signaling that involves endocytic trafficking and lysosome-mediated degradation of the mature, fully phosphorylated protein.
Source: Journal of Biological Chemistry
Language: English
Subfield: Cell Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
Awards: Regulation of cyclin D1 expression in the intestine, G168441794, PKC ISOZYMES AND INTESTINAL EPITHELIAL GROWTH CONTROL, G448474933, G5989231044, G6444510900, Drug Development and Cancer Treatments, Regulation of cyclin D1 expression in the intestine, G9000108264, G9000182468, G9000243664, Roswell Park Cancer Center Support Grant, Buffett Cancer Center Support Grant
OpenAlex ID: W2007688447