Binding of paxillin to alpha4 integrins modifies integrin-dependent biological responses.
The alpha4 integrins are indispensable for embryogenesis, haematopoiesis and immune responses, possibly because alpha4 regulates cellular functions differently from other integrins through its cytoplasmic tail. We used novel mimics of the alpha4 tail to identify molecules that could account for alpha4-specific signalling. Here we report that the alpha4 tail, but not several other alpha-subunit tails, binds tightly to the signalling adaptor paxillin. Paxillin physically associated with alpha4 integrins in Jurkat T cells at high stoichiometry, and joining the alpha4 tail to alphaIIb resulted in a complex of integrin alphaIIbbeta3 with paxillin. This association markedly enhanced the rates of alphaIIbbeta3-dependent phosphorylation of focal adhesion kinase and cell migration. It also reduced cell spreading, focal adhesion and stress fibre formation. A point mutation within the alpha4 tail that disrupts paxillin binding reversed all of these effects. Furthermore, alpha4beta1-dependent adhesion to VCAM-1 led to spreading of mouse embryonic fibroblasts derived from paxillin-null but not from wild-type mice. Thus, the tight association of paxillin with the alpha4 tail leads to distinct biochemical and biological responses to integrin-mediated cell adhesion.
Liu
S
S
Department of Vascular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Thomas
S M
SM
Woodside
D G
DG
Rose
D M
DM
Kiosses
W B
WB
Pfaff
M
M
Ginsberg
M H
MH
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D016466:CHO Cells; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002465:Cell Movement; D006224:Cricetinae; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D039441:Integrin alpha4; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D060588:LIM Domain Proteins; D051379:Mice; D018716:Molecular Mimicry; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014157:Transcription Factors; D014443:Tyrosine / Q000378:metabolism
D015703:Antigens, CD; D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins; C112251:LPXN protein, human; C504469:Lpxn protein, mouse; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; C496062:Pxn protein, mouse; D011993:Recombinant Fusion Proteins; C490351:TGFB1I1 protein, human; C090090:Tgfb1i1 protein, mouse; D014157:Transcription Factors; D039441:Integrin alpha4; D014443:Tyrosine