Biology subjects

Soto, M. C.

Publications and source records attributed to Soto, M. C..

4 recordsLinked to original sources

bioRxiv2025

The C. elegans WASH complex supports epithelial polarity by promoting endosomal sorting of Cadherin

Epithelial polarity requires polarized distribution of the apical adhesion complex that connects cells through the Cadherin transmembrane protein. Cadherin is intimately linked to the actin cytoskeleton through alpha catenin, which directly binds F-actin to set up the apical actin belt. Branched actin is formed when the Arp2/3 complex is activated by Nucleation Promoting Factors. C. elegans has three Nucleation Promoting Factors, WASP, WAVE and WASH. Our studies showed that WAVE-dependent branched actin promotes apical transport of Cadherin, including apically-directed transport of RAB-11-enriched endosomes. However, the contribution of other Nucleation Promoting Factors to Cadherin polarity has not been examined. The C. elegans WASH complex is not well described. Here we characterize components of the WASH complex, and confirm that CO5G5.2, despite being highly divergent, is the functional FAM21 component in C. elegans. We show that the WASH complex is enriched at early and recycling endosomes in the adult intestine, where it supports retrograde Cadherin transport. Our findings demonstrate that individual branched actin regulators promote specific transport steps, and identify WASH function at RME-1/EHD-enriched endosomes as an important contributor to Cadherin polarity and cargo sorting in a mature epithelium. Significance Statement*C. elegans has three known NPF (nucleation promoting factor) complexes to activate Arp2/3: WAVE, WASP and WASH. However, the role of C. elegans WASH complex in intracellular transport was unreported, and the essential component, FAM21, was not identified. *We show that C. elegans C05G5.2 is a likely FAM21 ortholog, since it functions in collaboration with other WASH components in retrograde transport. Loss of WASH components reduced epithelial polarity, while the cargo Cadherin was mis-sorted from early endosomes. *WASH branched actin polarizes epithelia using a functional FAM21 ortholog to promote sorting of retrograde cargo, including Cadherin.

cell biology↗

bioRxiv2023

CED-5/CED-12 (DOCK/ELMO) can promote and inhibit F-actin formation via distinct motifs that target different GTPases

Coordinated activation and inhibition of F-actin supports the movements of morphogenesis. Understanding the proteins that regulate F-actin is important, since these proteins are mis-regulated in diseases like cancer. Our studies of C. elegans embryonic epidermal morphogenesis identified the GTPase CED-10/Rac1 as an essential activator of F-actin. However, we need to identify the GEF, or Guanine-nucleotide Exchange Factor, that activates CED-10/Rac1 during embryonic cell migrations. The two-component GEF, CED-5/CED-12, is known to activate CED-10/Rac1 to promote cell movements that result in the engulfment of dying cells during embryogenesis, and a later cell migration of the larval Distal Tip Cell. It is believed that CED-5/CED-12 powers cellular movements of corpse engulfment and DTC migration by promoting F-actin formation. Therefore, we tested if CED-5/CED-12 was involved in embryonic migrations, and got a contradictory result. CED-5/CED-12 definitely support embryonic migrations, since their loss led to embryos that died due to failed epidermal cell migrations. However, CED-5/CED-12 inhibited F-actin in the migrating epidermis, the opposite of what was expected for a CED-10 GEF. To address how CED-12/CED-5 could have two opposing effects on F-actin, during corpse engulfment and cell migration, we investigated if CED-12 harbors GAP (GTPase Activating Protein) functions. A candidate GAP region in CED-12 faces away from the CED-5 GEF catalytic region. Mutating a candidate catalytic Arginine in the CED-12 GAP region (R537A) altered the epidermal cell migration function, and not the corpse engulfment function. A candidate GEF region on CED-5 faces towards Rac1/CED-10. Mutating Serine-Arginine in CED-5/DOCK predicted to bind and stabilize Rac1 for catalysis, resulted in loss of both ventral enclosure and corpse engulfment. Genetic and expression studies showed the GEF and GAP functions act on different GTPases. Thus, we propose CED-5/CED-12 support the cycling of multiple GTPases, by using distinct domains, to both promote and inhibit F-actin nucleation. Author SummaryGTPases in their active state promote actin nucleation that drives cellular events, from cell migrations, to cell shape changes, to cell-cell interactions. To function correctly, GTPases need to cycle from the active, GTP-bound state, to the inactive, GDP-bound state. This cycle is supported by Guanine-nucleotide Exchange Factors, or GEFs, that support activation as GDP is switched for GTP, and GTPase-Activating Proteins, or GAPs that support hydrolysis back to the GDP bound state. The Rac1/CED-10 GTPase has a well-studied GEF, CED-5/CED-12, that promotes Rac1 activation during cell engulfment of dying cells. Here we tested if CED-5/CED-12 also functioned as the activator, or GEF for Rac1 during embryonic cell migrations. Surprisingly, CED-5/CED-12 behaved completely opposite to what was expected during this cell migration. Therefore, we investigated if CED-5/CED-12 could harbor a GAP function. Comparing models of human and C. elegans protein structures suggested a putative GAP region, which we mutated to show that CED-12 likely functions as a GAP. Genetic and gene expression tests identify other GTPases, CDC-42 and RHO-1, regulated by this newly uncovered CED-12 GAP function. This places CED-5/CED-12 at a central position, where it can support the cycling of multiple GTPases, and both promote and inhibit F-actin nucleation.

cell biology↗

bioRxiv2019

RhoGAP RGA-8 supports morphogenesis in C. elegans by polarizing epithelia through CDC-42

CDC-42 regulation of non-muscle myosin/NMY-2 is required for polarity maintenance in the one-cell embryo of C. elegans. CDC-42 and NMY-2 regulate polarity throughout embryogenesis, but their contribution to later events of morphogenesis are less understood. We have shown that epidermal enclosure requires the GTPase CED-10/Rac1 and WAVE/Scar complex, its effector, to promote protrusions that drive enclosure through the branch actin regulator Arp2/3. Our analysis here of RGA-8, a homolog of SH3BP1/Rich1/ARHGAP17/Nadrin, with BAR and RhoGAP motifs, suggests it regulates CDC-42, so that NMY-2 promotes two events of epidermal morphogenesis: ventral enclosure and elongation. Genetic and molecular data suggest RGA-8 regulates CDC-42, and the CDC-42 effectors WSP-1 and MRCK-1, in parallel to F-BAR proteins TOCA-1 and TOCA-2. The RGA-8-CDC-42-WSP-1 pathway enriches myosin in migrating epidermal cells during ventral enclosure. We propose TOCA proteins and RGA-8 use BAR domains to localize and regenerate CDC-42 activity, thus regulating F-actin levels, through the branched actin regulator WSP-1, and myosin polarity through the myosin kinase MRCK-1. Regulated CDC-42 thus polarizes epithelia, to control cell migrations and cell shape changes of embryonic morphogenesis. SummaryRGA-8, a protein with membrane binding and actin regulatory motifs, promotes embryonic morphogenesis by localizing active CDC-42 in developing epithelia, thus controlling actin and actin motors during cell movements.

developmental biology↗

bioRxiv2018

The RhoGAP myosin 9/HUM-7 integrates membrane signals to modulate Rho/RHO-1 during embryonic morphogenesis in C. elegans

During embryonic morphogenesis, cells and tissues undergo dramatic movements under the control of F-actin regulators. Our studies of epidermal cell migrations in developing C. elegans embryos have identified multiple plasma membrane signals that regulate the Rac GTPase, thus regulating WAVE and Arp2/3 complexes, to promote branched F-actin formation and polarized enrichment. We describe here a pathway that acts in parallel to Rac to transduce membrane signals to control epidermal F-actin through the GTPase Rho. Rho contributes to epidermal migrations through effects on underlying neuroblasts. Here we identify signals to regulate Rho in the epidermis. HUM-7, the C. elegans homolog of human Myo9A and Myo9B, regulates F-actin dynamics during epidermal migrations, by controlling Rho. Genetics and biochemistry support that HUM-7 behaves as GAP for the Rho GTPase, so that loss of HUM-7 enhances Rho-dependent epidermal cell behaviors. We identify SAX-3/ROBO as an upstream signal that contributes to attenuated Rho activation through its regulation of HUM-7/Myo9. These studies identify a new role for Rho during epidermal cell migrations, and suggest that Rho activity is regulated by SAX-3/ROBO acting on the RhoGAP HUM-7.

developmental biology↗