['Activity of voltage-gated K(+) (K(v)) channels controls membrane potential (E(m)) that regulates cytosolic free Ca(2+) concentration ([Ca(2+)](cyt)) by regulating voltage-dependent Ca(2+) channel function. A rise in [Ca(2+)](cyt) in pulmonary artery smooth muscle cells (PASMCs) triggers vasoconstriction and stimulates PASMC proliferation. Whether c-Jun, a transcription factor that stimulates cell proliferation, affects K(v) channel activity in PASMCs was investigated.', 'Infection of primary cultured PASMCs with an adenoviral vector expressing c-jun increased the protein level of c-Jun and reduced K(v) currents (I(K(V))) compared with control cells (infected with an empty adenovirus). Using single-cell reverse transcription-polymerase chain reaction, we observed that the mRNA level of Kv1.5 and the current density of I(K(V)) were both attenuated in c-jun-infected PASMCs compared with control cells and cells infected with antisense c-jun. Overexpression of c-Jun also upregulated protein expression of Kvbeta(2) and accelerated I(K(V)) inactivation. Furthermore, E(m) was more depolarized and [(3)H]thymidine incorporation was greater in PASMCs infected with c-jun than in control cells and cells infected with antisense c-jun.'] Does c-Jun decrease voltage-gated K ( + ) channel activity in pulmonary artery smooth muscle cells?