Cdc42 Contributes to Phorbol Ester-Induced Ca2+-Independent Contraction of Pulmonary Artery Smooth Muscle

Abstract

ABSTRACT. We determined the contribution of the Rho family of low molecular GTP-binding proteins to phorbol ester-induced contraction in swine pulmonary artery smooth muscle. In Ca 2+ -free medium containing 1 mM EGTA, 12-deoxyphorbol 13-isobutyrate (DPB, 1 µM), a protein kinase C (PKC) activator, elicited sustained contractions, which were not inhibited by treatment with verapamil, a voltagedependent Ca 2+ channel antagonist, and Y27632, a Rho-associated kinase inhibitor. Immunoblot analysis showed three PKC isoforms (α, ε, and ζ) and two Rho GTPases (RhoA and Cdc42) in both cytosolic and the membrane fractions from quiescent strips. DPB (1 µM) significantly induced PKCα and ε to translocate from the cytosolic to the membrane fraction in Ca 2+ -free medium. DPB also elicited the translocation of Cdc42, but not RhoA to the membrane fraction. Similarly, in the experiment for measurement of Rho GTPase activity by pull-down assay, DPB (1 µM) significantly increased the activity of Cdc42 in Ca 2+ -free medium. Norepinephrine (NE, 10 µM) stimulated the redistribution of RhoA from the cytosolic to the membrane fraction in swine pulmonary artery smooth muscle. In contrast, NE did not alter the subcellular distributions of Cdc42 and the PKC isoforms. These results indicate that phorbol ester evokes PKC-mediated Ca 2+ -independent contraction via a Rho GTPase pathway, especially Cdc42, in smooth muscle from swine pulmonary arteries. KEY WORDS: Ca 2+ -independent contraction, Cdc42, protein kinase C, pulmonary artery smooth muscle.

Cdc42 and Rac1 are major contributors to the saturated fatty acid-stimulated JNK pathway in hepatocytes

“…Possible targets for DAG include the PKC family of protein kinases, consistent with previous studies that placed MLK3 downstream of PKC [18]. Interestingly, it has been shown that phorbol ester-treatment leads to PKC-dependent activation of Cdc42 and Rac1 [8]. This mechanism could contribute to the activation of Cdc42 and Rac1 by SFA.…”

ADP Ribosylation Factor 6 Promotes Contraction and Proliferation, Suppresses Apoptosis and Is Specifically Inhibited by NAV2729 in Prostate Stromal Cells

“…Major functions of ARF6 include cytoskeletal organization and actin remodeling, roles in endocytosis and vesicular trafficking, cell adhesion, and completion of mitotic cytokinesis in different cell types (D'Souza-Schorey and Chavrier, 2006;Donaldson, 2002;Hongu and Kanaho, 2014;Humphreys et al, 2013;Klein et al, 2006;Luton, 2005;Schafer et al, 2000;Schweitzer and D'Souza-Schorey, 2005). Accordingly, it promotes processes based on actin assembly and cytoskeletal organization, including migration, branching and outgrowth in neuronal cells, filopodia extension, platelet-mediated clot formation and thrombosis, or tumor angiogenesis and metastasis (Charles et al, 2016;Choi et al, 2005;Gauthier-Campbell et al, 2004;Hiroi et al, 2006;Hongu et al, 2016;Miura et al, 2016;Torii et al, 2010;Urban et al, 2016). With NAV2729, a small molecule inhibitor with presumed specificity for ARF6 is available (Yamauchi et al, 2017;Yoo et al, 2016).…”

Regulation of smooth muscle contraction by monomeric non‐RhoA GTPases

“…To the best of our knowledge, however, this was the only study directly reporting the role of CDC42 in smooth muscle contraction, that is, by showing smooth muscle contraction of intact tissues. Although other studies repeatedly suggested a similar role and suggested involved mechanisms, this evidence stayed preliminary and included demonstration of Cdc42 activation by contractile agonists and Cdc42 induced actin organization in smooth muscle cells (Choi et al, 2005; Fediuk, Sikarwar, Nolette, & Dakshinamurti, 2014; Q. F. Li & Tang, 2009; Tang & Gunst, 2004; Tang, Zhang, & Gunst, 2005; Zhang, Huang, & Gunst, 2016). Consequently, it has been assumed that Cdc42 promotes smooth muscle contraction by actin polymerization and filament organization but not via MLC phosphorylation (Figure 1), what involves most probably Wiskott–Aldrich Syndrome protein family members (Puetz et al, 2009).…”