title: FAM123A binds to microtubules and inhibits the guanine nucleotide exchange factor ARHGEF2 to decrease actomyosin contractility.
abstract: The FAM123 gene family comprises three members: FAM123A, the tumor suppressor WTX (also known as FAM123B), and FAM123C. WTX is required for normal development and causally contributes to human disease, in part through its regulation of β-catenin-dependent WNT signaling. The roles of FAM123A and FAM123C in signaling, cell behavior, and human disease remain less understood. We defined and compared the protein-protein interaction networks for each member of the FAM123 family by affinity purification and mass spectrometry. Protein localization and functional studies suggest that the FAM123 family members have conserved and divergent cellular roles. In contrast to WTX and FAM123C, we found that microtubule-associated proteins were enriched in the FAM123A protein interaction network. FAM123A interacted with and tracked with the plus end of dynamic microtubules. Domain interaction experiments revealed a "SKIP" amino acid motif in FAM123A that mediated interaction with the microtubule tip tracking proteins end-binding protein 1 (EB1) and EB3--and therefore with microtubules. Cells depleted of FAM123A showed compartment-specific effects on microtubule dynamics, increased actomyosin contractility, larger focal adhesions, and decreased cell migration. These effects required binding of FAM123A to and inhibition of the guanine nucleotide exchange factor ARHGEF2, a microtubule-associated activator of RhoA. Together, these data suggest that the SKIP motif enables FAM123A, but not the other FAM123 family members, to bind to EB proteins, localize to microtubules, and coordinate microtubule dynamics and actomyosin contractility.
authors.affiliation: Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA.
authors.forename: Priscila F
authors.initials: PF
authors.lastname: Siesser
authors.forename: Marta
authors.initials: M
authors.lastname: Motolese
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Walker
authors.forename: Dennis
authors.initials: D
authors.lastname: Goldfarb
authors.forename: Kelly
authors.initials: K
authors.lastname: Gewain
authors.forename: Feng
authors.initials: F
authors.lastname: Yan
authors.forename: Rima M
authors.initials: RM
authors.lastname: Kulikauskas
authors.forename: Andy J
authors.initials: AJ
authors.lastname: Chien
authors.forename: Linda
authors.initials: L
authors.lastname: Wordeman
authors.forename: Michael B
authors.initials: MB
authors.lastname: Major
mesh_terms: D000205:Actomyosin / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism*; D020816:Amino Acid Motifs / Q000235:genetics; D002846:Chromatography, Affinity; D022001:Focal Adhesions / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors*; D006801:Humans; D013058:Mass Spectrometry; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D025941:Protein Interaction Mapping; D064067:Rho Guanine Nucleotide Exchange Factors; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism*
chemical_list: C570412:AMER2 protein, human; C577356:ARHGEF2 protein, human; D048868:Adaptor Proteins, Signal Transducing; D020662:Guanine Nucleotide Exchange Factors; C500985:MAPRE1 protein, human; D008869:Microtubule-Associated Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D025521:Tumor Suppressor Proteins; D000205:Actomyosin