title: The C-terminal domain of Rac1 contains two motifs that control targeting and signaling specificity.
abstract: Rho-like GTPases control a wide range of cellular functions such as integrin- and cadherin-mediated adhesion, cell motility, and gene expression. The hypervariable C-terminal domain of these GTPases has been implicated in membrane association and effector binding. We found that cell-permeable peptides, encoding the C termini of Rac1, Rac2, RhoA, and Cdc42, interfere with GTPase signaling in a specific fashion in a variety of cellular models. Pull-down assays showed that the C terminus of Rac1 does not associate to either RhoGDI or to Pak. In contrast, the C terminus of Rac1 (but not Rac2 or Cdc42) binds to phosphatidylinositol 4,5-phosphate kinase (PIP5K) via amino acids 185-187 (RKR). Moreover, Rac1 associates to the adapter protein Crk via the N-terminal Src homology 3 (SH3) domain of Crk and the proline-rich stretch in the Rac1 C terminus. These differential interactions mediate Rac1 localization, as well as Rac1 signaling, toward membrane ruffling, cell-cell adhesion, and migration. These data show that the C-terminal, hypervariable domain of Rac1 encodes two distinct binding motifs for signaling proteins and regulates intracellular targeting and differential signaling in a unique and non-redundant fashion.
authors.affiliation: Sanquin Research at CLB and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam 1066 CX, The Netherlands.
authors.forename: Paula B
authors.initials: PB
authors.lastname: van Hennik
authors.forename: Jean Paul
authors.initials: JP
authors.lastname: ten Klooster
authors.forename: Jon R
authors.initials: JR
authors.lastname: Halstead
authors.forename: Carlijn
authors.initials: C
authors.lastname: Voermans
authors.forename: Eloise C
authors.initials: EC
authors.lastname: Anthony
authors.forename: Nullin
authors.initials: N
authors.lastname: Divecha
authors.forename: Peter L
authors.initials: PL
authors.lastname: Hordijk
mesh_terms: D016475:3T3 Cells; D000199:Actins / Q000737:chemistry; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002448:Cell Adhesion; D002460:Cell Line; D002465:Cell Movement; D004285:Dogs; D005347:Fibroblasts / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000737:chemistry; D018922:HL-60 Cells; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013997:Time Factors; D020830:rac1 GTP-Binding Protein / Q000737:chemistry*; D018909:src Homology Domains
chemical_list: D000199:Actins; D010455:Peptides; D020558:GTP Phosphohydrolases; D020830:rac1 GTP-Binding Protein