title: AF6 negatively regulates Rap1-induced cell adhesion.
abstract: AF6 is involved in the connection of membrane-associated proteins to the actin cytoskeleton. It binds to Ras-like small GTPases and is suggested to be an effector of both Ras and Rap. Here we show that knockdown of AF6 in T cells by RNA interference enhanced Rap1-induced integrin-mediated cell adhesion, whereas overexpression of AF6 had the opposite effect. Interestingly, AF6-induced inhibition of cell adhesion correlated with an increase in RapGTP levels. Like AF6, protein KIAA1849 contains a Ras association domain and interacted with Rap1. However, KIAA1849 did not inhibit Rap1-induced cell adhesion. We concluded that AF6 is a negative regulator of Rap-induced cell adhesion. We proposed that AF6 inhibits Rap-mediated cell adhesion by sequestering RapGTP in an unproductive complex and thus prevents the interaction of Rap1 not only with effectors that mediate adhesion but also with Rap GTPase-activating proteins. Thus, AF6 may buffer RapGTP in resting T cells and maintain them in a non-adherent state.
authors.affiliation: Department of Physiological Chemistry and Centre of Biomedical Genetics, University Medical Centre, Utrecht 3508 AB, The Netherlands.
authors.forename: Zhongchun
authors.initials: Z
authors.lastname: Zhang
authors.forename: Holger
authors.initials: H
authors.lastname: Rehmann
authors.forename: Leo S
authors.initials: LS
authors.lastname: Price
authors.forename: Jurgen
authors.initials: J
authors.lastname: Riedl
authors.forename: Johannes L
authors.initials: JL
authors.lastname: Bos
mesh_terms: D015153:Blotting, Western; D002448:Cell Adhesion; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000378:metabolism; D019169:Jurkat Cells; D016547:Kinesins / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*
chemical_list: C095516:AFDN protein, human; D016023:Integrins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; D009218:Myosins; D016547:Kinesins; D020827:rap1 GTP-Binding Proteins