Male Drosophila reproductive glands secrete exosomes in a BMP-dependent manner that fuse with sperm after mating and suppress female remating.

In Drosophila, posterior deposition of oskar (osk) mRNA in oocytes is critical for both pole cell and abdomen formation. Exon junction complex components, translational regulation factors, and other proteins form an RNP complex that is essential for directing osk mRNA to the posterior of the oocyte. Until now, it has not been clear whether the mRNA degradation machinery is involved in regulating osk mRNA deposition. Here we show that Drosophila decapping protein 1, dDcp1, is a posterior group gene required for the transport of osk mRNA. In oocytes, dDcp1 is localized posteriorly in an osk mRNA position- and dosage-dependent manner. In nurse cells, dDcp1 colocalizes with dDcp2 and Me31B in discrete foci that may be related to processing bodies (P bodies), which are sites of active mRNA degradation. Thus, as well as being a general factor required for mRNA decay, dDcp1 is an essential component of the osk mRNP localization complex.

Background Glutamine (Gln) is an abundant nutrient used by cancer cells. Breast cancers cells and particularly triple-receptor negative breast cancer (TNBC) are reported to be dependent on Gln to produce the energy required for survival and proliferation. Despite intense research on the role of the intracellular Gln pathway, few reports have focussed on Gln transporters in breast cancer and TNBC. Methods The role and localisation of the Gln transporter SLC38A2/SNAT2 in response to Gln deprivation or pharmacological stresses was examined in a panel of breast cancer cell lines. Subsequently, the effect of SLC38A2 knockdown in Gln-sensitive cell lines was analysed. The prognostic value of SLC38A2 in a cohort of breast cancer was determined by immunohistochemistry. Results SLC38A2 was identified as a strongly expressed amino acid transporter in six breast cancer cell lines. We confirmed an autophagic route of degradation for SLC38A2. SLC38A2 knockdown decreased Gln consumption, inhibited cell growth, induced autophagy and led to ROS production in a subgroup of Gln-sensitive cell lines. High expression of SLC38A2 protein was associated with poor breast cancer specific survival in a large cohort of patients (p = 0.004), particularly in TNBC (p = 0.02). Conclusions These results position SLC38A2 as a selective target for inhibiting growth of Gln-dependent breast cancer cell lines.

Exosomes are secreted nanovesicles with potent signalling activity that are initially formed as intraluminal vesicles (ILVs) in late Rab7‐positive multivesicular endosomes, and also in recycling Rab11a‐positive endosomes, particularly under some forms of nutrient stress. The core proteins of the Endosomal Sorting Complex Required for Transport (ESCRT) participate in exosome biogenesis and ILV‐mediated destruction of ubiquitinylated cargos. Accessory ESCRT‐III components have reported roles in ESCRT‐III‐mediated vesicle scission, but their precise functions are poorly defined. They frequently only appear essential under stress. Comparative proteomics analysis of human small extracellular vesicles revealed that accessory ESCRT‐III proteins, CHMP1A, CHMP1B, CHMP5 and IST1, are increased in Rab11a‐enriched exosome preparations. We show that these proteins are required to form ILVs in Drosophila secondary cell recycling endosomes, but unlike core ESCRTs, they are not involved in degradation of ubiquitinylated proteins in late endosomes. Furthermore, CHMP5 knockdown in human HCT116 colorectal cancer cells selectively inhibits Rab11a‐exosome production. Accessory ESCRT‐III knockdown suppresses seminal fluid‐mediated reproductive signalling by secondary cells and the growth‐promoting activity of Rab11a‐exosome‐containing EVs from HCT116 cells. We conclude that accessory ESCRT‐III components have a specific, ubiquitin‐independent role in Rab11a‐exosome generation, a mechanism that might be targeted to selectively block pro‐tumorigenic activities of these vesicles in cancer.