Up‐Regulation of Cell Surface Insulin Receptor by Protein Kinase C‐α in Adrenal Chromaffin Cells

摘要: Our previous study showed that treatment of cultured bovine adrenal chromaffin cells with phorbol 12, 13-dibutyrate (PDBu) or 12-O-tetradecanoylphorbol 13-acetate (TPA) caused a rapid ( 15 h) translocation both conventional (c) protein kinase C-α (PKC-α) and novel PKC-e (but not atypical PKC-ζ) from cytosol to membranes, whereas thymeleatoxin (TMX) increased the similar but selective membrane association only cPKC-α. In present study, chronic (≥12 PDBu raised cell surface 125I-insulin binding without altering KD value ; it developed in concentration (EC50 = 1.9 nM)-and time (t1/2 14.6 h)-dependent manner, reaching its maximum 115% increase at 48 h. Either TPA (30 nM) TMX 6.4 also by 97 88%, biologically inactive 4α-TPA had no effect. The increasing effect nM for 24 on was significantly blocked, even when H7, an inhibitor PKC, added 8 h after initiation treatment. Concurrent brefeldin A, vesicular transport trans-Golgi network, cycloheximide, synthesis, 5,6-dichlorobenzimidazole riboside, RNA abolished PDBu-induced increment binding. Western blot analysis, using antibody against β-subunit insulin receptor, 2.3 levels receptor precursor (~190 kDa t1/2 7.1 15.4 h), causing their almost 52 59% rises, respectively, Northern analysis revealed mRNAs ~35% as soon 3 h, producing monophasic peak ~76% increases All these effects mRNA were entirely prevented simultaneous Go6976, cPKC. These results suggest long-term activation cPKC-α up-regulates density via transcriptional/translational events.