title: SH2-Bbeta is a Rac-binding protein that regulates cell motility.
abstract: The Src homology 2 (SH2) domain-containing protein SH2-Bbeta binds to and is a substrate of the growth hormone (GH) and cytokine receptor-associated tyrosine kinase JAK2. SH2-Bbeta also binds, via its SH2 domain, to multiple activated growth factor receptor tyrosine kinases. We have previously implicated SH2-Bbeta in GH and platelet-derived growth factor regulation of the actin cytoskeleton. We extend these findings by establishing a potentiating effect of SH2-Bbeta on GH-dependent cell motility and defining regions of SH2-Bbeta required for this potentiation. Time-lapse video microscopy, phagokinetic, and/or wounding assays demonstrate reduced movement of cells overexpressing SH2-Bbeta lacking an intact SH2 domain because of a point mutation or a C-terminal truncation. An N-terminal proline-rich domain (amino acids 85-106) of SH2-Bbeta is required for inhibition of cellular motility by SH2 domain-deficient mutants. Co-immunoprecipitation experiments indicate that Rac binds to this domain. GH is shown to activate endogenous Rac, and dominant negative mutants of SH2-Bbeta are shown to inhibit membrane ruffling induced by constitutively active Rac. These findings suggest that SH2-Bbeta is an adapter protein that facilitates actin rearrangement and cellular motility by recruiting Rac and potentially Rac-regulating, Rac effector, or other actin-regulating proteins to activated cytokine (e.g. GH) and growth factor receptors.
authors.affiliation: Department of Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0622, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Diakonova
authors.forename: David R
authors.initials: DR
authors.lastname: Gunter
authors.forename: James
authors.initials: J
authors.lastname: Herrington
authors.forename: Christin
authors.initials: C
authors.lastname: Carter-Su
mesh_terms: D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001435:Bacteriophages / Q000378:metabolism; D016466:CHO Cells; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism* / Q000502:physiology*; D002460:Cell Line; D002465:Cell Movement; D006224:Cricetinae; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D005799:Genes, Dominant; D006801:Humans; D007150:Immunohistochemistry; D053614:Janus Kinase 2; D007700:Kinetics; D051379:Mice; D018715:Microscopy, Video; D008954:Models, Biological; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D013997:Time Factors; D014945:Wound Healing; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018076:DNA, Complementary; D011518:Proto-Oncogene Proteins; C518910:SH2B1 protein, human; C115327:Sh2bpsm1 protein, mouse; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D020744:rac GTP-Binding Proteins