Biology subjects

Skorobogata, O.

Publications and source records attributed to Skorobogata, O..

4 recordsLinked to original sources

bioRxiv2026

The AGEF-1/ARF-1 GTPase/AP-1 trafficking pathway differentially regulates LIN-12/Notch signaling in a tissue specific manner in C. elegans

LIN-12/Notch signaling regulates C. elegans vulval development via cell fate specifications in the gonad and epidermis. In the somatic gonad LIN-12/Notch activity specifies the anchor cell (AC) versus ventral uterine cell (VU) fates, with VU receiving more signal. The AC secretes epidermal growth factor (EGF) which induces the underlying vulval precursor cells (VPCs) to adopt vulval fates. In the VPCs the secondary vulval fates are specified by LIN-12/Notch activity. We previously reported that the AGEF-1, an Arf GEF homologous to ArfGEF1 and ArfGEF2, the ARF-1 GTPase, and the adaptor protein complex 1 (AP-1) inhibit LET-23/EGF receptor (EGFR) signaling in the VPCs by antagonizing LET-23/EGFR basolateral localization. Here we report that AGEF-1, ARF-1 and AP-1 regulate LIN-12/Notch signaling during somatic gonad and vulval development. The lin-12(n302) partial gain-of-function causes a potent Vulvaless phenotype due to a lack of AC specification. We demonstrate that loss of AGEF-1, ARF-1 or AP-1 restored the AC fate in lin-12(n302) animals, indicating that AGEF-1/ARF-1/AP-1 promotes LIN-12/Notch signaling in the somatic gonad. Interestingly, loss of AGEF-1, ARF-1 or AP-1 also induced ectopic vulval secondary fates in lin-12(n302) animals, indicating that AGEF-1/ARF-1/AP-1 inhibits LIN-12/Notch in the VPCs. Using a LIN-12/Notch biosensor we demonstrate that loss of UNC-101/AP-1 results in decreased signaling in the VU cell and increased signaling in the VPCs that correspond with decreased expression levels of LIN-12/Notch and LAG-1/DSL ligand in the presumptive AC and VU while also causing increased apical localization of LIN-12/Notch in the VPCs. We hypothesize that the differential regulation of LIN-12/Notch signaling could reflect different trafficking pathways in epithelial cells (VPCs) versus non-epithelial cells (AC and VU). Our results indicate that the AGEF-1/ARF-1/AP-1 trafficking pathway maintains the VPC cell fate patterning by limiting both LET-23/EGFR and LIN-12/Notch signaling. Author summaryCell signaling and membrane trafficking are highly interconnected processes whereby membrane trafficking can regulate signal transduction pathways and vice versa. We previously demonstrated that the ARF-1 GTPase, the downstream AP-1 clathrin adaptor and upstream activator AGEF-1 antagonize the membrane trafficking of the Epidermal Growth Factor Receptor (EGFR) and hence signaling during C. elegans vulva induction. Strong loss of the ARF-1 GTPase pathway resulted in ectopic vulval induction. Here we demonstrate that the ARF-1 GTPase pathway differentially regulates Notch signaling to regulate vulva induction. In the somatic gonad it promotes Notch signaling to regulate the specification of the anchor cell which secretes the inductive signal. In the vulva precursor cells, the ARF-1 GTPase pathway antagonizes Notch signaling which cooperates with EGFR signaling to induce the vulval cell fates. We hypothesize that the differential regulation of Notch signaling by the ARF-1 GTPase pathway could be a result of more complex membrane trafficking pathways in polarized epithelial cells (vulva precursors) versus non-epithelial cells in the developing somatic gonad. Thus, the AGEF-1/ARF-1/AP-1 antagonizes both EGFR and Notch signaling in ensuring that only three of the six vulval precursor cells adopt are induced.

cell biology↗

bioRxiv2026

An activating mutation in AGEF-1, a putative Arf GEF, causes yolk extrusion from C. elegans embryos

C. elegans AGEF-1, an ortholog of human ARFGEF1 and ARFGEF2, functions with ARF-1, ARF-5 and the AP-1 clathrin adaptor to regulate membrane trafficking. Similar phenotypes induced by the agef-1(vh4[E1028K]) allele and agef-1(RNAi) suggested that agef-1(vh4) was a hypomorph. Here we report that agef-1(vh4) results in extrusion of yolk from the embryo. This is suppressed by RNAi of agef-1, arf-1, arf-5 but not AP-1. Based on structure of the yeast AGEF-1 ortholog, Sec7p, the E1028K change is predicted to activate AGEF-1. We propose that Arf GTPase cycling is required to regulate trafficking with AP-1 but not with Arf effectors regulating yolk trafficking.

cell biology↗

bioRxiv2024

Centralspindlin promotes C. elegans anchor cell specification, vulva induction and morphogenesis

Caenorhabditis elegans vulval development is a relatively simple model of organ development whereby a signal from the overlying gonad induces three epithelial cells to undergo three rounds of cell division to generate 22 cells that make up the vulva. Specification of the vulva cell fates requires coordination between cell division and cell signaling via LIN-12/Notch and LET-23/EGFR pathways in the somatic gonad and the underlying epithelium. Here we characterize the positive regulation of vulval development by the centralspindlin complex, a conserved cytokinesis regulator. Centralspindlin, a heterotetramer of ZEN-4/KIF23 and CYK-4/RacGAP1, is essential for completion of cytokinesis during early embryonic cell divisions. We found that centralspindlin is required in the somatic gonad for division of somatic gonad precursor cells and hence specification of the LIN-3/EGF-secreting anchor cell critical for LET-23/EGFR-mediated vulval induction. However, the requirements for centralspindlin for cytokinesis during postembryonic development are incomplete as a binucleate anchor cell is frequently specified. The presence of the binucleate anchor cell correlates with vulva induction and demonstrates that LIN-12/Notch signaling, required for anchor cell specification, and LET-23/EGFR signaling, required for vulva induction, is largely functional in these cells. Centralspindlin is also partially required for cytokinesis of the vulval cells where it regulates vulva morphogenesis rather than induction. We also found that the GAP domain of CYK-4/RacGAP1 required for contractile ring assembly during embryonic division is not essential for vulval development. Thus, there appears to be different requirements for centralspindlin during postembryonic development of the somatic gonad and vulva as compared to early embryogenesis.

developmental biology↗

bioRxiv2024

Phosphorylation on serine 72 modulates Rab7A palmitoylation and retromer recruitment

AbstractThe small GTPase Rab7A has a key role in regulating membrane trafficking at late endosomes. By interacting with several different effectors, this small GTPase controls late endosome mobility, orchestrates fusion events between late endosomes and lysosomes, and participates in the formation of and regulates the fusion between autophagosomes and lysosomes. Rab7A is also responsible for the spatiotemporal recruitment of retromer, which is required for the endosome-to-TGN retrieval of cargo-receptors such as sortilin and CI-MPR. Recently several post-translational modifications have been shown to modulate Rab7A functions, including palmitoylation, ubiquitination and phosphorylation. Here we show that phosphorylation of Rab7A at serine 72 is important to modulate its interaction with retromer, as the non-phosphorylatable Rab7AS72A mutant is not able to interact with and recruit retromer to late endosomes. We have previously shown that Rab7A palmitoylation is also required for efficient retromer recruitment. We found that palmitoylation of Rab7AS72A is reduced compared to the wild-type protein, suggesting an interplay between S72 phosphorylation and palmitoylation in regulating the Rab7A/retromer interaction. Finally, we identify NEK7 as the kinase required to phosphorylate Rab7A to promote retromer binding and recruitment.

cell biology↗