Integration of signal pathways for stretch-dependent growth and differentiation in vascular smooth muscle.
The vascular smooth muscle phenotype is regulated by environmental factors, such as mechanical forces, that exert effects on signaling to differentiation and growth. We used the mouse portal vein in organ culture to investigate stretch-dependent activation of Akt, ERK, and focal adhesion kinase (FAK), which have been suggested to be involved in the regulation of stretch-dependent protein synthesis. The role of actin polymerization in these signaling events was examined using the actin-stabilizing agent jasplakinolide. Stretch caused a biphasic activation of FAK at 5-15 min and 24-72 h, which may reflect first a direct phosphorylation of preexisting focal adhesions followed by a rearrangement of focal adhesions to accommodate for the increased mechanical load. Phosphorylation of ERK was increased by acute stretch but then decreased, and Akt did not have a distinct peak in stretch-induced phosphorylation. Inhibition of ERK, phosphatidylinositol 3-kinase, or mammalian target of rapamycin reduced global but not contractile protein synthesis with maintained stretch sensitivity. Stabilization of actin filaments with jasplakinolide, in unstretched portal veins, resulted in increased ERK phosphorylation and global protein synthesis as well as the synthesis of contractile proteins. In contrast, stretch during culture with jasplakinolide did not affect FAK phosphorylation or contractility. Therefore, remodeling of smooth muscle cells to adapt to stretch requires a dynamic cytoskeleton.
Albinsson
Sebastian
S
Vascular Physiology Group, Dept of Experimental Medical Science, Lund University, BMC D12, Lund, Sweden.
Hellstrand
Per
P
D000199:Actins / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation; D049109:Cell Proliferation; D003285:Contractile Proteins / Q000096:biosynthesis*; D047630:Depsipeptides / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D005260:Female; D051417:Focal Adhesion Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D040542:Mechanotransduction, Cellular / Q000187:drug effects; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D009924:Organ Culture Techniques; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011169:Portal Vein / Q000166:cytology / Q000378:metabolism; D011311:Pressoreceptors / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D013314:Stress, Mechanical; D013997:Time Factors; D014661:Vasoconstriction
D000199:Actins; D003285:Contractile Proteins; D047630:Depsipeptides; D004791:Enzyme Inhibitors; D048049:Extracellular Signal-Regulated MAP Kinases; D051417:Focal Adhesion Kinase 1; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; C057531:jasplakinolide; C496051:Ptk2 protein, mouse