title: Adapter protein SH2B1beta binds filamin A to regulate prolactin-dependent cytoskeletal reorganization and cell motility.
abstract: Prolactin (PRL) regulates cytoskeletal rearrangement and cell motility. PRL-activated Janus tyrosine kinase 2 (JAK2) phosphorylates the p21-activated serine-threonine kinase (PAK)1 and the Src homology 2 (SH2) domain-containing adapter protein SH2B1β. SH2B1β is an actin-binding protein that cross-links actin filaments, whereas PAK1 regulates the actin cytoskeleton by different mechanisms, including direct phosphorylation of the actin-binding protein filamin A (FLNa). Here, we have used a FLNa-deficient human melanoma cell line (M2) and its derivative line (A7) that stably expresses FLNa to demonstrate that SH2B1β and FLNa are required for maximal PRL-dependent cell ruffling. We have found that in addition to two actin-binding domains, SH2B1β has a FLNa-binding domain (amino acids 200-260) that binds directly to repeats 17-23 of FLNa. The SH2B1β-FLNa interaction participates in PRL-dependent actin rearrangement. We also show that phosphorylation of the three tyrosines of PAK1 by JAK2, as well as the presence of FLNa, play a role in PRL-dependent cell ruffling. Finally, we show that the actin- and FLNa-binding-deficient mutant of SH2B1β (SH2B1β 3Δ) abolished PRL-dependent ruffling and PRL-dependent cell migration when expressed along with PAK1 Y3F (JAK2 tyrosyl-phosphorylation-deficient mutant). Together, these data provide insight into a novel mechanism of PRL-stimulated regulation of the actin cytoskeleton and cell motility via JAK2 signaling through FLNa, PAK1, and SH2B1β. We propose a model for PRL-dependent regulation of the actin cytoskeleton that integrates our findings with previous studies.
authors.affiliation: Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606-3390, USA.
authors.forename: Leah
authors.initials: L
authors.lastname: Rider
authors.forename: Maria
authors.initials: M
authors.lastname: Diakonova
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D020816:Amino Acid Motifs; D001665:Binding Sites; D045744:Cell Line, Tumor; D002465:Cell Movement; D022081:Cell Surface Extensions / Q000378:metabolism; D003285:Contractile Proteins / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism*; D064448:Filamins; D006801:Humans; D053614:Janus Kinase 2 / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011388:Prolactin / Q000494:pharmacology* / Q000502:physiology; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D021381:Protein Transport; D054462:p21-Activated Kinases / Q000378:metabolism
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D003285:Contractile Proteins; D064448:Filamins; D008840:Microfilament Proteins; D020033:Protein Isoforms; C518910:SH2B1 protein, human; D011388:Prolactin; C507924:JAK2 protein, human; D053614:Janus Kinase 2; C515903:PAK1 protein, human; D054462:p21-Activated Kinases