title: Junctional Rab13-binding protein (JRAB) regulates cell spreading via filamins.
abstract: We previously showed that Rab13 and its effector protein, junctional Rab13-binding protein (JRAB)/molecules interacting with CasL-like 2 (MICAL-L2), regulate junctional development by modulating cell adhesion molecule transport and actin cytoskeletal reorganization in epithelial cells. Here, we investigated how JRAB regulates reorganization of the actin cytoskeleton in NIH3T3 fibroblasts, in an attempt to obtain novel insights into the mechanism of JRAB action. To this end, we expressed mutant proteins that adopt a constitutively open or closed state and then examined effect on cellular morphology of the resulting actin cytoskeletal reorganization. Expression of the JRABΔCT mutant (constitutively 'closed' state) induced stress fibers, whereas expression of the JRABΔCC mutant (constitutively 'open' state) caused cell spreading with membrane ruffles. Next, we identified the proteins involved in JRAB-induced rearrangement of actin cytoskeleton leading to morphological changes. In NIH3T3 cells expressing HA-JRABΔCC, filamin, an actin cross-linking protein, coimmunoprecipitated with HA-JRABΔCC. Expression of ASB2 induced degradation of all three filamin isoforms and inhibited the JRABΔCC-induced cell spreading. Consistent with our previous results, actinin-1/-4 were also immunoprecipitated with HA-JRABΔCC. However, actinin-1/-4 have no effect on the cell spreading regulated by JRABΔCC. These data suggest that JRAB contributes to the rearrangement of the actin cytoskeleton during cell spreading via filamins.
authors.affiliation: Department of Biochemistry, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, 770-8503, Japan.
authors.forename: Ayuko
authors.initials: A
authors.lastname: Sakane
authors.forename: Ahmed
authors.initials: A
authors.lastname: Alamir Mahmoud Abdallah
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Nakano
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Honda
authors.forename: Toshio
authors.initials: T
authors.lastname: Kitamura
authors.forename: Issei
authors.initials: I
authors.lastname: Imoto
authors.forename: Natsuki
authors.initials: N
authors.lastname: Matsushita
authors.forename: Takuya
authors.initials: T
authors.lastname: Sasaki
mesh_terms: D000185:Actinin / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D064448:Filamins / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins; D009154:Mutation; D041681:NIH 3T3 Cells; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D017434:Protein Structure, Tertiary; D022502:Stress Fibers / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D064448:Filamins; C512298:JRAB protein, mouse; D008840:Microfilament Proteins; D020033:Protein Isoforms; D000185:Actinin