Disruption of actin-myosin interactions results in the inhibition of focal adhesion assembly in Xenopus XR1 glial cells.
In the present study we have investigated the role of actin-myosin interactions in regulating focal adhesion assembly in Xenopus XR1 glial cells. Actin-myosin interactions, stress fiber formation, and focal adhesion assembly are thought to allow cells to exert tension in the surrounding extracellular matrix, a process essential during morphogenesis and wound healing. Immunocytochemical analysis has revealed that myosin heavy chain-A (MHC-A), the predominant isoform in XR1 cells, was distributed in a filamentous pattern in the central region but was more diffuse towards the cell periphery. Myosin heavy chain-A-like immunoreactivity (IR) partially colocalized with phalloidin stained F-actin microfilaments in XR1 cells but not with microtubules. Furthermore, MHC-A-IR colocalized with immunoreactivity for beta1 integrin receptors and vinculin at focal adhesions located more centrally along the ventral surface of the cells. The partial colocalization of MHC-A with the F-actin cytoskeleton, as well as at focal adhesions, provides evidence that actin-myosin interactions may be involved in regulating focal adhesion assembly and stabilization. To examine this possibility, we have used drugs shown to inhibit cell contractility: the kinase inhibitors H7 and HA100, and 2,3-butanedione 2-monoxime (BDM), which inhibits muscle and nonmuscle ATPase activity. Compared to control cultures, those treated with the inhibitors exhibited a dose-dependent decrease in the percentage of cells that displayed focal adhesions. In addition, these cells also displayed disrupted actin cytoskeletons and a similar disruption in myosin filaments. Taken together, these results provide evidence for an important role of actin-myosin generated forces during focal adhesion assembly in glial cells.
Folsom
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Department of Zoology and Genetics, Iowa State University, Ames 50011, USA.
Sakaguchi
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D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D000199:Actins / Q000502:physiology*; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D003599:Cytoskeleton / Q000378:metabolism; D003931:Diacetyl / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D007150:Immunohistochemistry; D019012:Integrin beta1 / Q000378:metabolism; D018613:Microscopy, Confocal; D018995:Myosin Heavy Chains / Q000378:metabolism / Q000502:physiology*; D009457:Neuroglia / Q000187:drug effects / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D016596:Vinculin / Q000378:metabolism; D014981:Xenopus
D000199:Actins; D004791:Enzyme Inhibitors; D019012:Integrin beta1; D016596:Vinculin; C004717:diacetylmonoxime; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D017346:Protein Serine-Threonine Kinases; D000251:Adenosine Triphosphatases; D018995:Myosin Heavy Chains; D003931:Diacetyl