Novel Role of Protein Kinase C-δ Tyr ³¹¹ Phosphorylation in Vascular Smooth Muscle Cell Hypertrophy by Angiotensin II

Abstract

Abstract-We have shown previously that activation of protein kinase C-␦ (PKC␦) is required for angiotensin II (Ang II)-induced migration of vascular smooth muscle cells (VSMCs). Here, we have hypothesized that PKC␦ phosphorylation at Tyr 311 plays a critical role in VSMC hypertrophy induced by Ang II. Immunoblotting was used to monitor PKC␦ phosphorylation at Tyr 311 , and cell size and protein measurements were used to detect hypertrophy in VSMCs. PKC␦ was rapidly (0.5 to 10.0 minutes) phosphorylated at Tyr 311 by Ang II. This phosphorylation was markedly blocked by an Src family kinase inhibitor and dominant-negative Src but not by an epidermal growth factor receptor kinase inhibitor. Ang II-induced Akt phosphorylation and hypertrophic responses were significantly enhanced in VSMCs expressing PKC␦ wild-type compared with VSMCs expressing control vector, whereas the enhancements were markedly diminished in VSMCs expressing a PKC␦ Y311F mutant. Also, these responses were significantly inhibited in VSMCs expressing kinase-inactive PKC␦ K376A compared with VSMCs expressing control vector. From these data, we conclude that not only PKC␦ kinase activation but also the Src-dependent Tyr 311 phosphorylation contributes to Akt activation and subsequent VSMC hypertrophy induced by Ang II, thus signifying a novel molecular mechanism for enhancement of cardiovascular diseases induced by Ang II. (Hypertension. 2008;51:232-238.)

Tandem Phosphorylation of Serines 221 and 318 by Protein Kinase Cδ Coordinates mRNA Binding and Nucleocytoplasmic Shuttling of HuR

“…PKC␦ is a ubiquitously expressed member of the Ca 2ϩ -independent family of new PKC isoforms implicated in diverse cell functions, including cell proliferation, cell migration, and cell survival (48). The translocation of PKC␦ to the nucleus is critical for cell responses induced by AngII (16,45) and various genotoxins and apoptotic stimuli (48) and relies on a bipartite nuclear localization sequence (NLS) in the PKC␦ protein (60). Although the stabilizing effects of HuR on ARE-bearing mRNA are important for protection of mRNA from cytoplasmic decay by the exosomal complex, HuR binding to target mRNA already occurs in the nucleus (19,32).…”

Independent β-Arrestin2 and Gq/Protein Kinase Cζ Pathways for ERK Stimulated by Angiotensin Type 1A Receptors in Vascular Smooth Muscle Cells Converge on Transactivation of the Epidermal Growth Factor Receptor

“…In VSMCs, PKC␦ has been known to be activated upon ANG stimulation leading to AKT activation (38) and PKC has been suggested to play a major role in AT1R-mediated ERK/Elk-1 activation via the Ras/MEK pathway (24). We showed that inhibition of PKC activity using chemical inhibitors or by depletion of its expression by RNAi inhibited G protein-dependent (early time point) AT1R-mediated ERK activation in VSMCs.…”

Regulation of Protein Kinase C function by phosphorylation on conserved and non-conserved sites

“…Phosphorylation of PKC at Tyr-313 by Src family kinases has also been reported in a variety of cell types in response to non-apoptotic stimuli [117][118][119]46,120,32,121,100]. While some of these studies have shown that phosphorylation at Tyr-313 is required for PKC function, one consequence of Tyr-313 phosphorylation is that it regulates the ability of the enzyme to autophosphorylate its own A-loop and thus fine-tune substrate specificity [32,46].…”