Kai Michael Schubert1, Jiehua Qiu1, Stephanie Blodow1, Margarethe Wiedenmann1, Lubomir T Lubomirov1, Gabriele Pfitzer1, Ulrich Pohl2, Holger Schneider1. 1. From the Walter Brendel Centre of Experimental Medicine, Biomedical Center of LMU, Ludwig Maximilian University of Munich, Germany (K.M.S., J.Q., S.B., M.W., U.P., H.S.); Munich Cluster for Systems Neurology (SyNergy), Germany (K.M.S., S.B., U.P., H.S.); Deutsches Zentrum für Herz- Kreislauf-Forschung (German Center for Cardiovascular Research), Partner Site Munich Heart Alliance, Munich, Germany (K.M.S., S.B., U.P., H.S.); and Institute of Vegetative Physiology, University of Cologne, Germany (L.T.L., G.P.). 2. From the Walter Brendel Centre of Experimental Medicine, Biomedical Center of LMU, Ludwig Maximilian University of Munich, Germany (K.M.S., J.Q., S.B., M.W., U.P., H.S.); Munich Cluster for Systems Neurology (SyNergy), Germany (K.M.S., S.B., U.P., H.S.); Deutsches Zentrum für Herz- Kreislauf-Forschung (German Center for Cardiovascular Research), Partner Site Munich Heart Alliance, Munich, Germany (K.M.S., S.B., U.P., H.S.); and Institute of Vegetative Physiology, University of Cologne, Germany (L.T.L., G.P.). upohl@mail.de.
Abstract
RATIONALE: Decreasing Ca2+ sensitivity of vascular smooth muscle (VSM) allows for vasodilation without lowering of cytosolic Ca2+. This may be particularly important in states requiring maintained dilation, such as hypoxia. AMP-related kinase (AMPK) is an important cellular energy sensor in VSM. Regulation of Ca2+ sensitivity usually is attributed to myosin light chain phosphatase activity, but findings in non-VSM identified changes in the actin cytoskeleton. The potential role of AMPK in this setting is widely unknown. OBJECTIVE: To assess the influence of AMPK on the actin cytoskeleton in VSM of resistance arteries with regard to potential Ca2+ desensitization of VSM contractile apparatus. METHODS AND RESULTS: AMPK induced a slowly developing dilation at unchanged cytosolic Ca2+ levels in potassium chloride-constricted intact arteries isolated from mouse mesenteric tissue. This dilation was not associated with changes in phosphorylation of myosin light chain or of myosin light chain phosphatase regulatory subunit. Using ultracentrifugation and confocal microscopy, we found that AMPK induced depolymerization of F-actin (filamentous actin). Imaging of arteries from LifeAct mice showed F-actin rarefaction in the midcellular portion of VSM. Immunoblotting revealed that this was associated with activation of the actin severing factor cofilin. Coimmunoprecipitation experiments indicated that AMPK leads to the liberation of cofilin from 14-3-3 protein. CONCLUSIONS: AMPK induces actin depolymerization, which reduces vascular tone and the response to vasoconstrictors. Our findings demonstrate a new role of AMPK in the control of actin cytoskeletal dynamics, potentially allowing for long-term dilation of microvessels without substantial changes in cytosolic Ca2+.
RATIONALE: Decreasing Ca2+ sensitivity of vascular smooth muscle (VSM) allows for vasodilation without lowering of cytosolic Ca2+. This may be particularly important in states requiring maintained dilation, such as hypoxia. AMP-related kinase (AMPK) is an important cellular energy sensor in VSM. Regulation of Ca2+ sensitivity usually is attributed to myosin light chain phosphatase activity, but findings in non-VSM identified changes in the actin cytoskeleton. The potential role of AMPK in this setting is widely unknown. OBJECTIVE: To assess the influence of AMPK on the actin cytoskeleton in VSM of resistance arteries with regard to potential Ca2+ desensitization of VSM contractile apparatus. METHODS AND RESULTS: AMPK induced a slowly developing dilation at unchanged cytosolic Ca2+ levels in potassium chloride-constricted intact arteries isolated from mouse mesenteric tissue. This dilation was not associated with changes in phosphorylation of myosin light chain or of myosin light chain phosphatase regulatory subunit. Using ultracentrifugation and confocal microscopy, we found that AMPK induced depolymerization of F-actin (filamentous actin). Imaging of arteries from LifeAct mice showed F-actin rarefaction in the midcellular portion of VSM. Immunoblotting revealed that this was associated with activation of the actin severing factor cofilin. Coimmunoprecipitation experiments indicated that AMPK leads to the liberation of cofilin from 14-3-3 protein. CONCLUSIONS: AMPK induces actin depolymerization, which reduces vascular tone and the response to vasoconstrictors. Our findings demonstrate a new role of AMPK in the control of actin cytoskeletal dynamics, potentially allowing for long-term dilation of microvessels without substantial changes in cytosolic Ca2+.
Authors: Toby Holmes; Andrew W Brown; Marie Suggitt; Lucy A Shaw; Lucy Simpson; Joseph P A Harrity; Gillian M Tozer; Chryso Kanthou Journal: Sci Rep Date: 2020-06-18 Impact factor: 4.379
Authors: Sandra Pütz; Lisa Sophie Barthel; Marina Frohn; Doris Metzler; Mohammed Barham; Galyna Pryymachuk; Oliver Trunschke; Lubomir T Lubomirov; Jürgen Hescheler; Joseph M Chalovich; Wolfram F Neiss; Manuel Koch; Mechthild M Schroeter; Gabriele Pfitzer Journal: J Gen Physiol Date: 2021-06-11 Impact factor: 4.086