Protein kinase C-dependent regulation of l-arginine transport activity in Caco-2 intestinal cells

Abstract

The regulation of plasma membrane l-arginine transport activity was investigated in differentiated and undifferentiated states of the human intestinal cell line, Caco-2. The sodium-independent, leucine-insensitive uptake of l-arginine measured in this study has been assigned by us previously to system y + in Caco-2 cells. Treatment of cells with serum-free media containing epidermal growth factor (EGF), transforming growth factor α (TGFα), or the protein kinase C (PKC) activator 12- O-tetradecanoylphorbol 13-acetate (TPA), stimulated system y + arginine transport activity in Caco-2 cells. Transport upregulation by these growth factors or by TPA was blocked by cycloheximide or the PKC inhibitor chelerythrine. Arginine uptake was diminished during the course of differentiation, attributable to a reduction in the transport system y + capacity ( V max) with no change in apparent affinity ( K m). TPA stimulated arginine uptake required at least 3 h of continual exposure, and increased the membrane's transport capacity ( V max) in both undifferentiated and differentiated cells. TPA elevated the diminished transport V max of differentiated cells TPA to the elevated V max value associated with undifferentiated cells. We conclude that upregulation of arginine transport is part of a pleiotropic response to EGF/TGFα, and that this involves PKC and de novo synthesis of polypeptides associated with system y + transport activity.