![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Vol. 14, Issue 4, 1418-1432, April 2003
and
*Le Centre de Recherche en Cancérologie de
l'Université Laval, L'Hôtel-Dieu de Québec,
Québec G1R 2J6, Canada; Oxidative stress induces in endothelial cells
a quick and transient coactivation of both stress-activated protein
kinase-2/p38 and extracellular signal-regulated kinase (ERK)
mitogen-activated protein kinases. We found that inhibiting the ERK
pathway resulted, within 5 min of oxidative stress, in a misassembly of
focal adhesions characterized by mislocalization of key proteins such
as paxillin. The focal adhesion misassembly that followed ERK
inhibition with the mitogen-activated protein kinase kinase (MEK)
inhibitor PD098059 (2'-amino-3'-methoxyflavone) or with a kinase
negative mutant of ERK in the presence of H2O2
resulted in a quick and intense membrane blebbing that was associated
with important damage to the endothelium. We isolated by
two-dimensional gel electrophoresis a PD098059-sensitive phosphoprotein
of 38 kDa that we identified, by mass spectrometry, as tropomyosin-1.
In fact, H2O2 induced a time-dependent
phosphorylation of tropomyosin that was sensitive to inhibition by
PD098059 and UO126
(1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butanediane). Tropomyosin phosphorylation was also induced by expression of a
constitutively activated form of MEK1 (MEKCA), which
confirms that its phosphorylation resulted from the activation of ERK.
In unstimulated cells, tropomyosin-1 was found diffuse in the cells,
whereas it quickly colocalized with actin and stress fibers upon
stimulation of ERK by H2O2 or by expression of
MEKCA. We propose that phosphorylation of tropomyosin-1
downstream of ERK by contributing to formation of actin filaments
increases cellular contractility and promotes the formation of focal
adhesions. Incidentally, ML-7
(1-[5iodonaphthalene-1-sulfonyl]homopiperazine, HCl), an
inhibitor of cell contractility, inhibited phosphorylation of
tropomyosin and blocked the formation of stress fibers and focal
adhesions, which also led to membrane blebbing in the presence of
oxidative stress. Our finding that tropomyosin-1 is phosphorylated downstream of ERK, an event that modulates its interaction with actin,
may lead to further understanding of the role of this protein in
regulating cellular functions associated with cytoskeletal remodeling.
Medical Research
Council Phosphorylation Unit, School of Life Sciences, University of
Dundee, Dundee DD1 5EH, United Kingdom;
Department of Cell and Developmental Biology,
Upstate Medical University, Syracuse, New York 13210;
§Department of Orthopaedic Surgery, Faculty of
Medicine, The University of Tokyo, Tokyo 113-0033, Japan; and
Faculté de Pharmacie, Université de
Montréal, Montréal H3C 3J7, Canada
This article has been cited by other articles:
|
|
 |
|
  K. Lange, M. Kammerer, F. Saupe, M. E. Hegi, S. Grotegut, E. Fluri, and G. Orend Combined Lysophosphatidic Acid/Platelet-Derived Growth Factor Signaling Triggers Glioma Cell Migration in a Tenascin-C Microenvironment Cancer Res., September 1, 2008; 68(17): 6942 - 6952. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Gunning, G. O'neill, and E. Hardeman Tropomyosin-Based Regulation of the Actin Cytoskeleton in Time and Space Physiol Rev, January 1, 2008; 88(1): 1 - 35. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. Houle, A. Poirier, J. Dumaresq, and J. Huot DAP kinase mediates the phosphorylation of tropomyosin-1 downstream of the ERK pathway, which regulates the formation of stress fibers in response to oxidative stress J. Cell Sci., October 15, 2007; 120(20): 3666 - 3677. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 V. S. Rao, L. R. La Bonte, Y. Xu, Z. Yang, B. A. French, and W. H. Guilford Alterations to myofibrillar protein function in nonischemic regions of the heart early after myocardial infarction Am J Physiol Heart Circ Physiol, July 1, 2007; 293(1): H654 - H659. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Cai Hydrogen peroxide regulation of endothelial function: Origins, mechanisms, and consequences Cardiovasc Res, October 1, 2005; 68(1): 26 - 36. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Somara, H. Pang, and K. N. Bitar Agonist-induced association of tropomyosin with protein kinase C{alpha} in colonic smooth muscle Am J Physiol Gastrointest Liver Physiol, February 1, 2005; 288(2): G268 - G276. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 V. D. Nair, T. Yuen, C. W. Olanow, and S. C. Sealfon Early Single Cell Bifurcation of Pro- and Antiapoptotic States during Oxidative Stress J. Biol. Chem., June 25, 2004; 279(26): 27494 - 27501. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Somara and K. N. Bitar Tropomyosin interacts with phosphorylated HSP27 in agonist-induced contraction of smooth muscle Am J Physiol Cell Physiol, June 1, 2004; 286(6): C1290 - C1301. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Bharadwaj, S. Hitchcock-DeGregori, A. Thorburn, and G. L. Prasad N Terminus Is Essential for Tropomyosin Functions: N-TERMINAL MODIFICATION DISRUPTS STRESS FIBER ORGANIZATION AND ABOLISHES ANTI-ONCOGENIC EFFECTS OF TROPOMYOSIN-1 J. Biol. Chem., April 2, 2004; 279(14): 14039 - 14048. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Samaj, F. Baluska, and H. Hirt From signal to cell polarity: mitogen-activated protein kinases as sensors and effectors of cytoskeleton dynamicity J. Exp. Bot., January 2, 2004; 55(395): 189 - 198. [Abstract] [Full Text] [PDF]
|
|
