title: Rho-kinase modulates the function of STEF, a Rac GEF, through its phosphorylation.
abstract: Rho family GTPases are key regulators of various physiological processes. Several recent studies indicated that the antagonistic relationship between Rho and Rac is essential for cell polarity and that the Rac activity is negatively regulated by Rho. In this study, we found that Rho-kinase, an effector of Rho, counteracted the Rac GEF STEF-induced Rac1 activation in COS7 cells. Rho-kinase phosphorylated STEF at Thr1662 in vitro, and Y-27632, a Rho-kinase inhibitor, suppressed lysophosphatidic acid-induced phosphorylation of STEF in PC12D cells. STEF interacted with specific molecules such as microtubule-associated protein 1B, and the phosphorylation of STEF by Rho-kinase diminished its interaction with these molecules. STEF promoted nerve growth factor-induced neurite outgrowth in PC12D cells, while the phosphomimic mutant of STEF had a weakened ability to enhance neurite outgrowth. Taken together, these results suggest that the phosphorylation of STEF by Rho-kinase exerts the inhibitory effect on the function of STEF.
authors.affiliation: Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, 65 Tsurumai, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Mikito
authors.initials: M
authors.lastname: Takefuji
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Mori
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Morita
authors.forename: Nariko
authors.initials: N
authors.lastname: Arimura
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishimura
authors.forename: Masanori
authors.initials: M
authors.lastname: Nakayama
authors.forename: Mikio
authors.initials: M
authors.lastname: Hoshino
authors.forename: Akihiro
authors.initials: A
authors.lastname: Iwamatsu
authors.forename: Toyoaki
authors.initials: T
authors.lastname: Murohara
authors.forename: Kozo
authors.initials: K
authors.lastname: Kaibuchi
authors.forename: Mutsuki
authors.initials: M
authors.lastname: Amano
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004252:DNA Mutational Analysis; D020662:Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D051379:Mice; D016501:Neurites / Q000502:physiology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017384:Sequence Deletion; D013912:Threonine / Q000235:genetics / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D054460:rho-Associated Kinases
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D047908:Intracellular Signaling Peptides and Proteins; C447620:Tiam2 protein, mouse; D013912:Threonine; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020830:rac1 GTP-Binding Protein