1. Adapter Protein SH2B1β Cross-Links Actin Filaments and Regulates Actin Cytoskeleton
- Author
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Leah Rider, Jiayun Lu, Brittany Brinley, Maria Diakonova, Jing Tao, and Stacy Snyder
- Subjects
Arp2/3 complex ,macromolecular substances ,Biology ,Article ,Mice ,Actin remodeling of neurons ,Endocrinology ,Cell Movement ,Animals ,Humans ,Protein Isoforms ,Pseudopodia ,Actin-binding protein ,Molecular Biology ,Cells, Cultured ,Cytoskeleton ,Adaptor Proteins, Signal Transducing ,Mice, Knockout ,Microvilli ,Microfilament Proteins ,Actin remodeling ,General Medicine ,Janus Kinase 2 ,Phosphoproteins ,Actin cytoskeleton ,Actins ,Cell biology ,biology.protein ,Mutant Proteins ,MDia1 ,Protein Multimerization ,Lamellipodium ,Cell Adhesion Molecules ,Filopodia ,Protein Binding - Abstract
The Src homology 2 (SH2) domain-containing adapter protein SH2B1beta plays a role in severe obesity, leptin and insulin resistance, and infertility. SH2B1beta was initially identified as a Janus tyrosine kinase 2 (JAK2) substrate, and it has been implicated in cell motility and regulation of the actin rearrangement in response to GH and platelet-derived growth factor. SH2B1beta is also required for maximal actin-based motility of Listeria. Here we have used a low-speed pelleting assay and electron microscopy to demonstrate that SH2B1beta has two actin-binding sites and that it cross-links actin filaments in vitro. Wild-type SH2B1beta localized to cell ruffles and along filopodia, but deletion of amino acids 150-200 (the first actin-binding site) led to mislocalization of the protein to filopodia tip complexes where it colocalized with vasodilator-stimulated phosphoprotein (VASP). Based on studies performed in VASP-deficient MVD7(-/-) cells, with or without green fluorescent protein-VASP reconstitution, we concluded that the proper intracellular localization of native SH2B1beta required the presence of the first SH2B1beta actin-binding site and VASP. Finally, we found that both SH2B1beta actin-binding domains were required for maximal GH- and prolactin-induced cell ruffling. Together, these results suggest that SH2B1beta functions as an adapter protein that cross-links actin filaments, leading to modulation of cellular responses in response to JAK2 activation.
- Published
- 2009