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Regulation of secretion during development

Invitation for undergraduate students can be found here

1) Regulation of the functional organisation of the early secretory pathway
A large part of our past activity has been to identify principles underlying the functional organisation of the early secretory pathway (ER exit site (ERES)-Golgi) in the Drosophila tissue cultured S2 cells [1, 2]. In this respect, we have characterised the Drosophila orthologue of the large hydrophilic protein Sec16 that is critical for the biogenesis and maintenance of ERES [3]. Recently, we have used an RNAi depletion approach of pre-selected putative ER proteins to identify new components involved this organisation [4].
      Considering the strong regulation of secretion by signalling [5], we have started a large project to elucidate the regulation of secretion by nutrient signalling in Drosophila S2 cells.

In particular, we have shown that secretion is actively inhibited by serum and amino-acid starvation that leads to the release of Sec16 away from ER membrane (serum starvation) and formation of reversible aggregates (amino-acid). This results in turn to the disassembly of the secretory pathway and secretion inhibition. We have identified the unconventional MAP kinase ERK7 as an important component involved in sensing the nutrient conditions [6]. we have now investigated the response of the early secretory pathway to amino-acid starvation and identified a novel stress assembly that we named Sec body [7].

2) Asymmetric distribution of mRNAs
Using methods to visualise RNA localisation at the ultrastructural level based on RNA in situ hybridisation coupled to immuno-EM on frozen sections that we have developed [8], we have investigated the localisation of gurken [9] and bicoid [10] RNAs in the Drosophila oocyte, both endogenous, injected and MS2 tagged.

In collaboration with the group of Ilan Davis (Oxford, UK), we have recently demonstrated that although both mRNAs reside in the same large cytoplasmic structures resembling Processing Bodies (PB) in stage 9 oocyte, their sub-compartmentalisation within PBs correlate with differential states of translation [11].

     We have also shown that a series of mRNAs encoding proteins of the secretory pathway are localised at the basal site of the Drosophila follicular epithelium at a very specific stage of development [12,13]. One of these mRNAs is dgrasp and we have recently shown that QKI, a member of the STAR family of RNA binding proteins, is required for its stability [14].

3) Classical and unconventional secretion
dgrasp mRNA encodes dGRASP, a peripheral protein of the Golgi apparatus [15], a compartment of the classical secretory pathway (ER>ER exit sites>Golgi>PM) [16]. In the last few years, however, GRASP has been shown to be required for the unconventional protein secretion including the Golgi bypass transmembrane protein delivery to the plasma membrane [12, 17, 18]. To understand the relevance of this pathway, we have generated a KO mouse for one of the mammalian homologue GRASP65 [19] .

4) Dynamic of junction proteins during epithelium remodeling
We have unravelled novel roles for gap junctions proteins at specific stages of development. The first is a role for Innexin 3 during dorsal closure of Drosophila embryo [20] and the second is a role for Inx7 in the cellularisation of the flour beetle Tribolium [21].
Furthermore, we have also investigated E-cadherin dynamics and fate during cell extrusion [22].


[1] Kondylis V et al (2007) Dev Cell 12:901; [2] Kondylis V and Rabouille C (2009). FEBS lett. 583:3827; [3] Ivan V et al (2008) Mol. Biol. Cell 19:4352; [4] Kondylis V et al (2011). PLOS One; 6: e17173; [5] Farhan H and Rabouille C (2011) J Cell Sci 124:171; [6] Zacharogianni M et al (2011) EMBO J 30:3684-700; [7] Zacharogianni M et al (2014). In revision at Elife. [8] Herpers B, Xanthakis D and Rabouille C (2010) Nat Protoc 5:678; [9] Delanoue R et al (2007) Dev Cell 13:523; [10] Weil T et al (2010) Development 137:169; [11] Weil T et al (2012) Nat Cell Biol 14:1305-13; [12] Schotman H, Karhinen L and Rabouille C (2008) Dev Cell 14:171-182; [13] Schotman H, Karhinen L and Rabouille C (2009) J Cell Sci. 122:2662; [14] Giuliani G et al (2013) Nucleic Acid Res 42(3):1970-86. [15] Vinke FP et al (2011) Biochem J 433:423; [16] Mellman I, and Warren W (2000) Cell 100:99. [17] Rabouille C et al (2012) J Cell Sci 125:5251-5; [18] Grieve AG and Rabouille C (2011) The Golgi book. CSH.
Veenendaal et al (2014). Biology Open. 3(6):431-43; [20] Giuliani F et al (2013) PLOS one 8:e69212; [21] van der Zee M et al (2013) in revision at Development; [22] Grieve A and Rabouille C (2014). J. Cell Science. 127:3331-46

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Undergraduate students
We welcome motivated undergraduate students to participate in one of these projects. Besides learning many cell biology techniques (tissue culture, Westerns, generating DNA constructs, transfections) as well as fly genetics, students can get familiar with imaging techniques depending on their own interests and experience.

If you are interested please contact  Catherine Rabouille