Predominant localization of phosphatidylserine at the cytoplasmic leaflet of the ER, and its TMEM16K-dependent redistribution.

TMEM16K, a membrane protein carrying 10 transmembrane regions, has phospholipid scramblase activity. TMEM16K is localized to intracellular membranes, but whether it actually scrambles phospholipids inside cells has not been demonstrated, due to technical difficulties in studying intracellular lipid distributions. Here, we developed a freeze-fracture electron microscopy method that enabled us to determine the phosphatidylserine (PtdSer) distribution in the individual leaflets of cellular membranes. Using this method, we found that the endoplasmic reticulum (ER) of mammalian cells harbored abundant PtdSer in its cytoplasmic leaflet and much less in the luminal leaflet, whereas the outer and inner nuclear membranes (NMs) had equivalent amounts of PtdSer in both leaflets. The ER and NMs of budding yeast also harbored PtdSer in their cytoplasmic leaflet, but asymmetrical distribution in the ER was not observed. Treating mouse embryonic fibroblasts with the Ca2+ ionophore A23187 compromised the cytoplasmic leaflet-dominant PtdSer asymmetry in the ER and increased PtdSer in the NMs, especially in the nucleoplasmic leaflet of the inner NM. This Ca2+-induced PtdSer redistribution was not observed in TMEM16K-null fibroblasts, but was recovered in these cells by reexpressing TMEM16K. These results indicate that, similar to the plasma membrane, PtdSer in the ER of mammalian cells is predominantly localized to the cytoplasmic leaflet, and that TMEM16K directly or indirectly mediates Ca2+-dependent phospholipid scrambling in the ER.

Efficacy of the Addition of Robot-assisted Radical Cystectomy with Extracorporeal Urinary Diversion after an Enhanced Recovery Protocol.

PURPOSE: It is unclear if robotic radical cystectomy with extracorporeal urinary diversion (eRARC) provides additional benefit when performed along with enhanced recovery after surgery (ERAS). We assessed the additional efficacy of eRARC in terms of perioperative outcomes. MATERIALS AND METHODS: We retrospectively assessed 143 patients undergoing radical cystectomy with urinary diversion between June 2010 and December 2021 at a single center. The patients were assigned to three groups: open radical cystectomy (ORC) with conventional recovery after surgery (CRAS) [Group A], ORC with ERAS [Group B], and eRARC with ERAS [Group C]. A propensity score-matched analysis was performed to evaluate how ERAS and eRARC affected outcomes respectively. Meanwhile, multivariable analysis was used to detect the predictors of prolonged length of hospital stay (LOS). RESULTS: The median LOS was shorter after ERAS and eRARC. In the propensity score-matched analysis, ERAS was linked to a significantly shorter median LOS (28.0 vs. 20.0 days, P < .001), but eRARC was not associated with a shorter LOS (19.0 vs. 17.5 days, P = .21). Neither ERAS nor eRARC were connected with a reduce in complication rate. Following multivariable analysis, ERAS was found to be independently associated with shorter LOS (OR=0.23, P < .001), but eRARC demonstrated no such correlation (OR=0.29, P = .096). CONCLUSION: ERAS had strong association with shorter LOS, although eRARC did not contribute to additional efficacy. Neither ERAS nor eRARC decreased the complication rate.