Caveolin scaffolding peptide-1 interferes with norepinephrine-induced PLC-β activation in cultured rat vascular smooth muscle cells

Caveolins are a family of integral membrane proteins implicated in various cell functions, including the organization and inactivation of signaling molecules of G protein-coupled receptors. We tested the ability of human caveolin scaffolding peptide-1 (CSP-1) to regulate norepinephrine-(NE) or histamine (HIS)-induced increases on intracellular calcium concentrations ([Ca²⁺]_i). In cultured rat vascular smooth muscle cells (VSMC), CSP-1 inhibited in a concentration-dependent manner NE- and HIS-induced increases in [Ca²⁺]_i. This effect can be explained by the fact that CSP-1 inhibited a common signaling pathway. We tested the ability of this peptide to decrease the activation of PLC-β3 and MAPK. CSP-1 inhibited the expression of the activated form of both enzymes, suggesting a direct effect of the peptide on the signaling cascade. CSP-1 readily enters VSMC in culture, as observed when FITC-conjugated CPS-1 is added to cell culture media. Taken together, these data suggest that CSP-1 blocks the effects of NE and HIS on [Ca²⁺]_i of VSMC by inhibiting the activation of PLC-β3 and MAPK.