ARF1-regulated coatomer directs the steady-state localization of protein kinase C epsilon at the Golgi apparatus

Abstract

Protein kinase C epsilon (PKCε) contributes to multiple signaling pathways affecting human disease. The function of PKCε requires it to undergo changes in subcellular distribution in response to signaling events. While the mechanisms underlying this translocation are incompletely understood it involves the receptor for activated C kinase protein (RACK2/β′-COP). This receptor also functions as a vesicle coat protein in the secretory pathway where it is regulated by the small GTP-binding protein ADP-ribosylation factor, ARF1. We inhibited ARF1 activation to test the requirement for RACK2/β′-COP in PKCε localization in NIH3T3 fibroblasts. We found that steady-state localization of PKCε at the Golgi complex requires ARF1-regulated RACK2/β′-COP function. By contrast, we did not observe any defects in phorbol ester-induced translocation when ARF1 was inhibited. We also found that PKCε bound to isolated membranes through two distinct mechanisms. One mechanism was dependent upon RACK2/β′-COP while a second was RACK2/β′-COP-independent and stimulated by phorbol esters. Finally, we show that RACK2/β′-COP affects the subcellular distribution of a constitutively active form of PKCε, in a manner similar to what we observed for wild-type PKCε. Together, our data support a role for RACK2/β′-COP in the steady-state localization of PKCε at the Golgi apparatus, which may be independent of its role during PKCε translocation to the cell surface.

Roles of Diacylglycerols and Ceramides in Hepatic Insulin Resistance

“…Although the technique commonly employed is relatively crude (the membrane fraction includes all membranous organelles and the plasma membrane), it may be further refined in the future. It is interesting to note that cell-based studies have implicated the Golgi, mitochondrion, and plasma membrane as sites of PKCε translocation [62]. A final important consideration for the DAG-PKCε hypothesis is that triglyceride hydrolysis by ATGL in the hepatocyte preferentially produces sn -1,3-DAG, which is incapable of activating PKC [63,64].…”

Ethanol-Induced Changes in PKCε: From Cell to Behavior

“…A recent study reported the PKCε-RACKε-β′-COP complex to travel to the GA via a small GTP-binding protein ADP-ribosylation factor (ARF-1)-mediated pathway in NIH3T3 cells in an unstimulated state. The same study also reported that phorbol ester-dependent transport of PKCε-RACKε to the membrane surface is coatomer independent (Peterson and Stamnes, 2013 ), suggesting that the role of the coatomer in PKCε transportation pertains to the Golgi alone.…”

A Catalog of Proteins Expressed in the AG Secreted Fluid during the Mature Phase of the Chinese Mitten Crabs (Eriocheir sinensis)

“…The coatomer protein complex (COP) is required for budding from Golgi membranes and is essential for the retrograde Golgi-to-ER transport of dilysine-tagged proteins. The complex also influences the Golgi structural integrity, as well as the processing, activity and endocytic recycling of LDL (low-density lipoprotein) receptors [ 66 ]. It is involved in the Golgi disassembly and reassembly processes during the cell cycle and in autophagy by playing a role in an early endosome function [ 65 ].…”