The N-terminal SH2 domains of Syk and ZAP-70 mediate phosphotyrosine-independent binding to integrin beta cytoplasmic domains.
Syk and ZAP-70 form a subfamily of nonreceptor tyrosine kinases that contain tandem SH2 domains at their N termini. Engagement of these SH2 domains by tyrosine-phosphorylated immunoreceptor tyrosine-based activation motifs leads to kinase activation and downstream signaling. These kinases are also regulated by beta3 integrin-dependent cell adhesion via a phosphorylation-independent interaction with the beta3 integrin cytoplasmic domain. Here, we report that the interaction of integrins with Syk and ZAP-70 depends on the N-terminal SH2 domain and the interdomain A region of the kinase. The N-terminal SH2 domain alone is sufficient for weak binding, and this interaction is independent of tyrosine phosphorylation of the integrin tail. Indeed, phosphorylation of tyrosines within the two conserved NXXY motifs in the integrin beta3 cytoplasmic domain blocks Syk binding. The tandem SH2 domains of these kinases bind to multiple integrin beta cytoplasmic domains with varying affinities (beta3 (Kd = 24 nm) > beta2 (Kd = 38 nm) > beta1 (Kd = 71 nm)) as judged by both affinity chromatography and surface plasmon resonance. Thus, the binding of Syk and ZAP-70 to integrin beta cytoplasmic domains represents a novel phosphotyrosine-independent interaction mediated by their N-terminal SH2 domains.
Woodside
Darren G
DG
Division of Vascular Biology, Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Obergfell
Achim
A
Talapatra
Anupam
A
Calderwood
David A
DA
Shattil
Sanford J
SJ
Ginsberg
Mark H
MH
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004792:Enzyme Precursors / Q000378:metabolism*; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000378:metabolism; D039641:Integrin beta Chains / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009532:Nickel / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020349:Surface Plasmon Resonance; D000072377:Syk Kinase; D013997:Time Factors; D051746:ZAP-70 Protein-Tyrosine Kinase; D018909:src Homology Domains
D004792:Enzyme Precursors; D039641:Integrin beta Chains; D047908:Intracellular Signaling Peptides and Proteins; D011993:Recombinant Fusion Proteins; D019000:Phosphotyrosine; D009532:Nickel; D005982:Glutathione Transferase; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; D051746:ZAP-70 Protein-Tyrosine Kinase