A screen for modifiers of RacGAP(84C) gain-of-function in the Drosophila eye revealed the LIM kinase Cdi/TESK1 as a downstream effector of Rac1 during spermatogenesis.
In Drosophila, RotundRacGAP/RacGAP(84C) is critical to retinal organisation and spermatogenesis. We show that eye-directed expression of RacGAP(84C) or its GTPase activating protein (GAP) domain induces a dominant rough eye phenotype which we used as a starting point in a gain-of-function screen to identify new partners of RacGAP(84C). Proteins known to function in Ras, Rho and Rac signalling were identified confirming the essential role of RacGAP(84C) in crosstalk between GTPases. Other potential RacGAP(84C) partners identified by the screen are implicated in signal transduction, DNA remodelling, cytoskeletal organisation, membrane trafficking and spermatogenesis. This latter class includes the serine/threonine kinase Center divider (Cdi), which is homologous to the human LIM kinase, Testis specific kinase 1 (TESK1), involved in cytoskeleton control through Cofilin phosphorylation. Eye-directed expression of cdi strongly suppressed the phenotypes induced by either RacGAP(84C) gain-of-function or by the dominant negative form of Rac1, Rac1N17. These results are consistent with Cdi being a specific downstream target of Rac1. We showed that Rac1 and cdi are both expressed in Drosophila testis and that homozygous Rac1 mutants exhibit poor fertility that is further reduced by introducing a cdi loss-of-function mutation in trans. Thus, results from a misexpression screen in the eye led us to a putative novel Rac1-Cdi-Cofilin pathway, regulated by RacGAP(84C), coordinating Drosophila spermatogenesis.
Raymond
Karine
K
CEA-Grenoble, Département de Réponse et Dynamique Cellulaires, UMR 5092, 17 rue des Martyrs, 38054 Grenoble CEDEX 9, France.
Bergeret
Evelyne
E
Avet-Rochex
Amélie
A
Griffin-Shea
Ruth
R
Fauvarque
Marie-Odile
MO
D051339:Actin Depolymerizing Factors; D000818:Animals; D003599:Cytoskeleton / Q000378:metabolism; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D005123:Eye / Q000201:enzymology* / Q000648:ultrastructure; D020690:GTPase-Activating Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D005799:Genes, Dominant; D017344:Genes, Insect; D006720:Homozygote; D007248:Infertility, Male / Q000235:genetics; D008297:Male; D008840:Microfilament Proteins; D016254:Mutagenesis, Insertional; D009928:Organ Specificity / Q000235:genetics; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D013091:Spermatogenesis; D013737:Testis / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D051339:Actin Depolymerizing Factors; D029721:Drosophila Proteins; D020690:GTPase-Activating Proteins; D008840:Microfilament Proteins; C434935:RacGAP84C protein, Drosophila; C119916:cdi protein, Drosophila; C097507:testis-specific protein kinase 1; D017346:Protein Serine-Threonine Kinases; D020830:rac1 GTP-Binding Protein