A single class II myosin modulates T cell motility and stopping, but not synapse formation

Abstract

Upon encountering an antigen, motile T cells stop crawling, change morphology and ultimately form an 'immunological synapse'. Although myosin motors are thought to mediate various aspects of this process, the molecules involved and their exact roles are not defined. Here we show that nonmuscle myosin heavy chain IIA, or MyH9, is the only class II myosin expressed in T cells and is associated with the uropod during crawling. MyH9 function is required for maintenance of the uropod and for T cell motility but is dispensable for synapse formation. Phosphorylation of MyH9 in its multimerization domain by T cell receptor-generated signals indicates that inactivation of this motor may be a key step in the 'stop' response during antigen recognition.

Inhibiting nonmuscle myosin II impedes inflammatory infiltration and ameliorates progressive renal disease

“…7,10 Consistent with previous reports, 13,14,17,18 NMII is expressed in all immune competent cells examined, including RAM, THP-1, and Jurkat. MCP-1-stimulated macrophages showed an evident physical association between actin and myosin ( Figure 1b).…”

“…11 It is a cell-permeable 1-phenyl-1-2-pyrrolidinone derivative that shows high affinity and selectivity toward NMII adenosine triphosphatase activity with minimal effects on activity of smooth muscle myosin II or other types of myosin. 12 Blebbistatin was recently found to mitigate the migration of a variety of immune competent cells, [13][14][15][16][17][18] suggesting that NMII is crucial for immunocyte motility. Consistently, a growing body of evidence reveals that indirect inactivation of NMII through inhibition of myosin light chain kinase 19,20 or Rho kinase 18,[21][22][23][24] impaired leukocyte migration and improved inflammation.…”

Myosin IIA is required for cytolytic granule exocytosis in human NK cells

“…Although synapse formation and conjugation were unimpaired, further experiments are required to fully evaluate the eff ect of myosin II inhibition on NK cell motility, especially as myosin IIA has previously been shown to regulate the motility of CD4 ϩ T cells ( 8 ). However, both treatment with PMA/ionomycin that is uniformly distributed within media and interaction with anti-CD16 mAb-coated plates are motility independent.…”

“…The discovery of blebbistatin (1-phenyl-1,2,3,4-tetrahydro-4-hydroxypyrrolo[2.3-b]-7-methylquinolin-4-one), which is a specifi c inhibitor of myosin II ATPase activity ( 7 ), has facilitated the study of myosin II function in immune cells. Inhibition of myosin II by blebbistatin in CD4 ϩ T cells impairs cell motility, but not IS formation ( 8 ). Moreover, inhibition of myosin II with the myosin light chain kinase inhibitor ML-9 (1-[5-chloronaphthalene-1-sulfonyl]-1H-hexahydro-1,4-diazepine hydrochloride) has been shown to inhibit NK cell cytotoxicity, but not eff ector -target conjugation ( 9 ).…”

Integrins in Cell Migration

“…In amoeboid cells RhoA-induced activation of ROCK mediates myosin light chain phosphorylation at the uropod resulting in the activation of myosin II (Eddy et al 2000;Xu et al 2003). Moreover, down-regulation of myosin heavy chain IIa using small interfering RNA (siRNA) inhibits uropod formation and motility of T cells (Jacobelli et al 2004). Although regulated uropod detachment is likely important for leukocyte motility, the precise function of the uropod in regulating leukocyte motility remains unknown.…”