Cskdifferentially regulatesSrc64during distinct morphological events inDrosophilagerm cells

Abstract

The Src family protein tyrosine kinases (SFKs) are crucial regulators of cellular morphology. In Drosophila, Src64 controls complex morphological events that occur during oogenesis. Recent studies have identified key Src64-dependent mechanisms that regulate actin cytoskeletal dynamics during the growth of actin-rich ring canals, which act as intercellular bridges between germ cells. By contrast, the molecular mechanisms that regulate Src64 activity levels and potential roles for Src64 in additional morphological events in the ovary have not been defined. In this report, we demonstrate that regulation of Src64 by Drosophila C-terminal-Src Kinase (Csk) contributes to the packaging of germline cysts by overlying somatic follicle cells during egg chamber formation. These results uncover novel roles for both Csk and Src64 in a dynamic event that involves adhesion, communication between cell types and control of cell motility. Strikingly, Src64 and Csk function in the germline to control packaging, not in migrating follicle cells, suggesting novel functions for this signaling cassette in regulating dynamic adhesion. In contrast to the role played by Csk in the regulation of Src64 activity during packaging, Csk is dispensable for ring canal growth control, indicating that distinct mechanisms control Src64 activity during different morphological events.

Maternal and zygotic requirements for src64 during Drosophila cellularization

“…src64 D17 deletes the first two noncoding exons . src64 KO deletes the entire src64 coding region (O'Reilly et al, 2006). src64 D404N is an amorphic allele for cellularization (Strong and Thomas,FIG.…”

“…src64 D17 , a mutation that deletes the first two exons of src64, has been used in many studies on src64 (Djagaeva et al, 2005;Dodson et al, 1998;Guarnieri et al, 1998;Kelso et al, 2002;Lu et al, 2004;Roulier et al, 1998;Thomas and Wieschaus, 2004). We suspected that src64 D17 mutants retain some src64 activity because a trace of Src64 protein was detected on Western blots , and the src64 KO knockout mutation causes more severe ring canal growth defects and egg-laying defects than the src64 D17 mutation (O'Reilly et al, 2006). We also observed more severe cellularization defects in src64 KO mutant embryos than in src64 D17 mutant embryos (Strong and Thomas, unpublished observations).…”

“…src64 is a Drosophila homologue of vertebrate c-src, a proto-oncogene encoding a nonreceptor tyrosine kinase that regulates adhesion, cell cycle progression, migration, apoptosis, development, angiogenesis, tumor invasion, and metastasis (Frame, 2002;Harrison, 2003;Thomas and Brugge, 1997;Tweedie et al, 2009;Yeatman, 2004). Both c-src and src64 have been implicated in regulating several microfilament cytoskeleton-associated cellular processes Frame et al, 2002;Guarnieri et al, 1998;O'Reilly et al, 2006;Roulier et al, 1998;Tateno et al, 2000;Thomas and Wieschaus, 2004;Thomas and Brugge, 1997).…”

Src family kinases are required for WNT5 signaling through the Derailed/RYK receptor in theDrosophilaembryonic central nervous system

“…Anti-PY434SRC64B antiserum was commercially generated and purified (Eurogentec) against the SRC64B peptide RVIADDEYCPKQG and its phosphorylated version (RVIADDEpYCPKQG) as described (O'Reilly et al, 2006) and verified as phosphopeptide-specific by ELISA and by its lack of staining on Src64B KO mutant embryos (data not shown). 293T cell lysate immunoprecipitations were performed using anti-c-SRC mAb (Upstate) and immunoblots were probed with anti-c-SRC or anti-HA to detect HA-tagged RYK.…”

Phospho-Signaling at Oocyte Maturation and Fertilization: Set Up for Embryogenesis and Beyond Part I. Protein Kinases

“…The Src64-Tec29 axis is also involved in microfilament contraction during cellularization, a Drosophila-specific phenomenon. Although the cellular target of Src64 phosphorylation is not yet clearly shown, its upstream regulators such as csk homolog-mediated phosphorylation and phosphoinositidedependent activation mechanism have been demonstrated (Dodson et al 1998;Lu et al 2004;O'Reilly et al 2006). …”