Role of GTP binding, isoprenylation, and the C-terminal α-helices in the inhibition of cell spreading by the interferon-induced GTPase, mouse guanylate-binding protein-2.
Interferon-γ pre-exposure inhibits Rac activation by either integrin engagement or platelet-derived growth factor treatment. Interferon-γ does this by inducing expression of the large guanosine triphosphatase (GTPase) mouse guanylate-binding protein (mGBP-2). Inhibiting Rac results in the retardation of cell spreading. Analysis of variants of mGBP-2 containing amino acid substitutions in the guanosine triphosphate (GTP) binding domain suggests that GTP binding, and possibly dimerization, of mGBP-2 is necessary to inhibit cell spreading. However, isoprenylation is also required. Removal of the N-terminal GTP-binding globular domain from mGBP-2 yields a protein with only the extended C-terminal α-helices that lacks enzymatic activity. The ability of the C-terminal α-helices alone to inhibit cell spreading suggests that this is the domain that interacts with the downstream effectors of mGBP-2. Interestingly, mGBP-2 can inhibit cell spreading whether it is geranylgeranylated or farnesylated. This study begins to define the properties of mGBP-2 responsible for inhibiting cell spreading.
Balasubramanian
Sujata
S
Department of Biological Sciences, University of Toledo , Toledo, Ohio.
Messmer-Blust
Angela F
AF
Jeyaratnam
Jonathan A
JA
Vestal
Deborah J
DJ
D016475:3T3 Cells; D019943:Amino Acid Substitution; D000818:Animals; D019204:GTP-Binding Proteins / Q000235:genetics / Q000276:immunology*; D006160:Guanosine Triphosphate / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007371:Interferon-gamma / Q000235:genetics / Q000276:immunology; D051379:Mice; D020125:Mutation, Missense; D010982:Platelet-Derived Growth Factor / Q000235:genetics / Q000276:immunology; D017368:Protein Prenylation / Q000235:genetics / Q000276:immunology*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000276:immunology*
D010982:Platelet-Derived Growth Factor; D007371:Interferon-gamma; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; C452200:Gbp2 protein, mouse; D020744:rac GTP-Binding Proteins