Biological characterization of Drosophila Rapgap1, a GTPase activating protein for Rap1.
The activity of Ras family proteins is modulated in vivo by the function of GTPase activating proteins, which increase their intrinsic rate of GTP hydrolysis. We have isolated cDNAs encoding a GAP for the Drosophila Rap1 GTPase. Drosophila Rapgap1 encodes an 850-amino acid protein with a central region that displays substantial sequence similarity to human RapGAP. This domain, when expressed in Escherichia coli, potently stimulates Rap1 GTPase activity in vitro. Unlike Rap1, which is ubiquitously expressed, Rapgap1 expression is highly restricted. Rapgap1 is expressed at high levels in the developing photoreceptor cells and in the optic lobe. Rapgap1 mRNA is also localized in the pole plasm in an oskar-dependent manner. Although mutations that completely abolish Rapgap1 function display no obvious phenotypic abnormalities, overexpression of Rapgap1 induces a rough eye phenotype that is exacerbated by reducing Rap1 gene dosage. Thus, Rapgap1 can function as a negative regulator of Rap1-mediated signaling in vivo.
Chen
F
F
Massachusetts General Hospital Cancer Center, Building 149, 13th Street, Charlestown, MA 02129, USA.
Barkett
M
M
Ram
K T
KT
Quintanilla
A
A
Hariharan
I K
IK
D000595:Amino Acid Sequence; D000818:Animals; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins; D004789:Enzyme Activation / Q000235:genetics; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D005786:Gene Expression Regulation; D017344:Genes, Insect; D006004:Glycogen Debranching Enzyme System / Q000378:metabolism*; D006801:Humans; D019476:Insect Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D020668:rap GTP-Binding Proteins
D029721:Drosophila Proteins; D020690:GTPase-Activating Proteins; D006004:Glycogen Debranching Enzyme System; D019476:Insect Proteins; D011506:Proteins; C484658:RAP1GAP protein, human; C109224:Rapgap1 protein, Drosophila; C020569:4 alpha-glucanotransferase; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins