Efficient EGFR signaling and dorsal–ventral axis patterning requires syntaxin dependent Gurken trafficking

Abstract

Vesicle trafficking plays a crucial role in the establishment of cell polarity in various cellular contexts, including axis-pattern formation in the developing egg chamber of Drosophila. The EGFR ligand, Gurken (Grk), is first localized at the posterior of young oocytes for anterior-posterior axis formation and later in the dorsal-anterior region for induction of the dorsal-ventral (DV) axis, but regulation of Grk localization by membrane trafficking in the oocyte remains poorly understood. Here, we report that Syntaxin-1A (Syx1A) is required for efficient trafficking of Grk protein for DV patterning. We show that Syx1A is associated with the Golgi membrane and is required for the transportation of Grk-containing vesicles along the microtubules to their dorsal anterior destination in the oocyte. Our studies reveal that the Syx1A dependent trafficking of Grk protein is required for efficient EGFR signaling during DV patterning.

Drosophila Hephaestus/Polypyrimidine Tract Binding Protein Is Required for Dorso-Ventral Patterning and Regulation of Signalling between the Germline and Soma

“…The dispersal of Grk throughout the oocyte in heph mutants suggests that Heph could function in the trafficking of Grk protein after translation [74],[77],[81],[82],[83],[84],[85]. There are a number of previously studied mutants, such as rab6 [83],[86], and syntaxin 1A ( Syx1A ) [84] in which grk mRNA localization is unaffected, but Grk protein is mislocalized. Furthermore, in these mutants, as is the case with heph , only the dorso-anterior localization and signalling of Grk protein is affected, and not the posterior localization or signalling during earlier stages of oogenesis.…”

“…This is thought to be a consequence of a lower threshold for EGFR activation by Grk signalling in the posterior follicle cells compared with the dorso-anterior follicle cells [74]. In null germline clones of the small GTPase Rab6, Grk mislocalizes to droplet-like structures throughout the ooplasm [83],[84] that colocalize with post-Golgi vesicle markers [83]. In hypomorphic germline clones of the Syx1A t-SNARE protein, Grk protein is also diffused throughout the ooplasm and partially colocalizes with Rab6 [84].…”

“…In null germline clones of the small GTPase Rab6, Grk mislocalizes to droplet-like structures throughout the ooplasm [83],[84] that colocalize with post-Golgi vesicle markers [83]. In hypomorphic germline clones of the Syx1A t-SNARE protein, Grk protein is also diffused throughout the ooplasm and partially colocalizes with Rab6 [84]. Localization of Grk protein at the dorso-anterior of the oocyte therefore depends upon membrane trafficking, and it is possible that Heph also functions to regulate and restrict Grk protein trafficking only to the dorso-anterior corner of the oocyte.…”

Polarized sorting of Patched enables cytoneme‐mediated Hedgehog reception in the Drosophila wing disc

“…The Gal4 drivers were as follows: ap.Gal4 (Calleja et al, 1996), hh.Gal4 (Tanimoto et al, 2000), ptc.Gal4 (Calleja et al, 1996), tub.Gal4 (BDSC5138) and actin>CD2>Gal4 (Pignoni & Zipursky, 1997) used to generate ectopic clones of the UAS line. The pUAStransgenes were as follows: UAS.ptc-GFP (Torroja et al, 2004), UAS.ihog-CFP (Bilioni et al, 2013), UAS.ihog-YFP (Callejo et al, 2011), UAS.tsp96F-HA (FlyORF003566), UAS.CD63-Cherry (a gift from Clive Wilson, Oxford University), UAS.CD63-GFP (Panakova et al, 2005), UAS.CD4-GFP (BDSC64315), UAS.nsyb-GFP (BDSC6921), UAS.syx1A-GFP (Tian et al, 2013), UAS.syt1-GFP (BDSC6926). The LexA driver was dpp.LexA (Yagi et al, 2010) to direct expression of LexO.nsyb-GFP (BDSC64315).…”

Modulation of Cell–Cell Interactions in Drosophila Oocyte Development

“…In addition, Syntaxin-1A, a member of the N-ethylmaleimide-sensitive factor (NSF) attachment protein receptor (SNARE) complex, is essential for trafficking of the Gurken protein. Syntaxin-1A is associated with the Golgi membrane and regulates transportation of Gurken-containing vesicles along polarized microtubules in the oocyte and enables polarized secretion [12]. Polarized microtubules exist in networks throughout the interconnected germ cells (reviewed in [62]), which facilitate polarized secretion of several molecules including Gurken, and is regulated by the activity of the small GTPase Rab6 [12,63,64].…”