Adenylate cyclase 5 and KCa1.1 channel are required for EGFR up-regulation of PCNA in native contractile rat basilar artery smooth muscle.

In synthetic phenotype vascular smooth muscle cells (VSMC), activation of epidermal growth factor (EGF) receptor (EGFR) induces a sustained increase in intermediate conductance K_Ca (int-K_Ca; K_Ca3.1) channels that is essential for proliferation. However, a comparable mechanism has not been identified in native contractile phenotype VSMC, which express large conductance K_Ca (maxi-K_Ca; K_Ca1.1) channels, not int-K_Ca channels. Using patch clamp of freshly isolated contractile VSMC from rat basilar artery, we found that EGF (100 ng ml^-1) caused hyperpolarization (7.9 ± 3.9 mV) due to activation of iberiotoxin-sensitive, maxi-K_Ca channels. The EGFR ligands EGF (100 ng ml^-1), transforming growth factor α (0.4 ng ml^-1) and heparin-binding EGF (100 ng ml^-1) all caused a 20% increase in maxi-K_Ca channel current that was blocked by AG-1478 or by knock-down of EGFR expression using cisterna magna infusion of antisense oligodeoxynucleotide (AS-ODN). In controls, EGFR knock-down, and EGFR gain-of-expression (angiotensin II hypertension), the increase in maxi-K_Ca current correlated with the abundance of EGFR protein expressed. The EGFR-mediated increase in maxi-K_Ca channel activity was blocked by inhibiting cAMP-dependent protein kinase (cAK) using KT-5720 or Rp-cAMP, or by inhibiting adenylate cyclase type 5 (AC-5) using 2′,5′-dideoxyadenosine or knock-down of AC-5 expression by intracisternal AS-ODN. Direct infusion of EGF into cisterna magna caused up-regulation of proliferating cell nuclear antigen (PCNA) in VSMC that was prevented by coinfusion of iberiotoxin or of AG-1478. Our data, which are consistent with the hypothesis that hyperpolarization is critical for a proliferative response, are the first to implicate AC-5 and maxi-K_Ca channels in gene activation related to EGFR signalling in native contractile VSMC. [ABSTRACT FROM AUTHOR]