After endocytosis, most cargo enters the pleiomorphic early endosomes in which sorting occurs. As endosomes mature, transmembrane cargo can be sequestered into inwardly budding vesicles for degradation, or can exit the endosome in membrane tubules for recycling to the plasma membrane, the recycling endosome, or the Golgi apparatus. Endosome to Golgi transport requires the retromer complex. Without retromer, recycling cargo such as the MIG‐14/Wntless protein aberrantly enters the degradative pathway and is depleted from the Golgi. Endosome‐associated clathrin also affects the recycling of retrograde cargo and has been shown to function in the formation of endosomal subdomains. Here, we find that the Caemorhabditis elegans endosomal J‐domain protein RME‐8 associates with the retromer component SNX‐1. Loss of SNX‐1, RME‐8, or the clathrin chaperone Hsc70/HSP‐1 leads to over‐accumulation of endosomal clathrin, reduced clathrin dynamics, and missorting of MIG‐14 to the lysosome. Our results indicate a mechanism, whereby retromer can regulate endosomal clathrin dynamics through RME‐8 and Hsc70, promoting the sorting of recycling cargo into the retrograde pathway.

Caenorhabditis elegans RAB-10 functions in endocytic recycling in polarized cells, regulating basolateral cargo transport in the intestinal epithelia and postsynaptic cargo transport in interneurons. Here we show binding of RAB-10 to EHBP-1, a CH-domain protein, and demonstrate a requirement for EHBP-1 in RAB-10–regulated transport in both of these tissues.

Caenorhabditis elegans RAB-10 and mammalian Rab10 are key regulators of endocytic recycling, especially in the basolateral recycling pathways of polarized epithelial cells. To understand better how RAB-10 contributes to recycling endosome function, we sought to identify RAB-10 effectors. One RAB-10-binding partner that we identified, CNT-1, is the only C. elegans homolog of the mammalian Arf6 GTPase-activating proteins ACAP1 and ACAP2. Arf6 is known to regulate endosome-to-plasma membrane transport, in part through activation of type I phophatidylinositol-4-phosphate 5 kinase. Here we show that CNT-1 binds to RAB-10 through its C-terminal ankyrin repeats and colocalizes with RAB-10 and ARF-6 on recycling endosomes in vivo. Furthermore, we find that RAB-10 is required for the recruitment of CNT-1 to endosomal membranes in the intestinal epithelium. Consistent with negative regulation of ARF-6 by RAB-10 and CNT-1, we found overaccumulation of endosomal phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2] in cnt-1 and rab-10 mutants and reduced endosomal PI(4,5)P2 levels in arf-6 mutants. These mutants produced similar effects on endosomal recruitment of the PI(4,5)P2-dependent membrane-bending proteins RME-1/Ehd and SDPN-1/Syndapin/Pacsin and resulted in endosomal trapping of specific recycling cargo. Our studies identify a RAB-10-to-ARF-6 regulatory loop required to regulate endosomal PI(4,5)P2, a key phosphoinositide in membrane traffic. membrane lipid | clathrin

Introduction Recent American College of Cardiology and European Society of Cardiology guidelines for syncope evaluation help distinguish high-cardiac risk patients from those with low-risk orthostatic and neurogenic syncope. Inpatient evaluation is recommended if at least one high-risk feature is present. Objective To assess guideline adherence and its impact on hospitalization in patients who presented with syncope before and after the introduction of guideline-based syncope protocol in the emergency department (ED). Methods All adult patients admitted to general medicine from the ED with the primary diagnosis of syncope in the months of October 2016 and October 2018 (before and after the introduction of syncope protocol in 2017). Electronic charts were retrospectively reviewed for high-risk cardiac features and orthostatic blood pressure measurement. Results Sixty patients were admitted for syncope in October 2016 (n = 32) and October 2018 (n = 28), out of which 33 (55%) were female and 47 (78.3%) were over age 50. Forty-five patients had at least one high-risk feature. Excluding one patient with an alternate diagnosis at discharge, 14 out of 60 patients (23.3%) admitted for syncope did not have any high-risk feature. Orthostatic blood pressure was measured in 3 patients (5%) in the ED and 27 patients (45%) later in the hospitalization. Six out of eight patients with implanted cardioverter-defibrillator or pacemaker had their devices interrogated. After the introduction of syncope protocol, there was an improvement in the proportion of high-risk patients admitted [68.7% (22/32) in October 2016 vs. 82.1% (23/28) in October 2018]. Conclusion Utilizing syncope protocol in the ED may improve guideline adherence, direct appropriate disposition, and reduce healthcare expenses.

No abstract