Ubiquitination is involved in PKC-mediated degradation of cell surface Kv1.5 channels.

The voltage-gated Kv1.5 potassium channel, conducting the ultra-rapid delayed rectifier K+ current (IKur) in human cells, plays important roles in the repolarization of atrial action potentials and regulation of the vascular tone. We previously reported that activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate (PMA) induces endocytic degradation of cell-surface Kv1.5 channels, and a point mutation removing the phosphorylation site, T15A, in the N terminus of Kv1.5 abolished the PMA-effect. In the present study, using mutagenesis, patch clamp recording, Western blot analysis, and immunocytochemical staining, we demonstrate that ubiquitination is involved in the PMA-mediated degradation of mature Kv1.5 channels. Since the expression of the Kv1.4 channel is unaffected by PMA treatment, we swapped the N- and/or C-termini between Kv1.5 and Kv1.4. We found that the N-terminus alone did not but both N- and C-termini of Kv1.5 did confer PMA sensitivity to mature Kv1.4 channels, suggesting the involvement of Kv1.5 C-terminus in the channel ubiquitination. Removal of each of the potential ubiquitination residue Lysine at position 536, 565, and 591 by Arginine substitution (K536R, K565R, and K591R) had little effect, but removal of all three Lysine residues with Arginine substitution (3K-R) partially reduced PMA-mediated Kv1.5 degradation. Furthermore, removing the cysteine residue at position 604 by Serine substitution (C604S) drastically reduced PMA-induced channel degradation. Removal of the three Lysines and Cys604 with a quadruple mutation (3K-R/C604S) or a truncation mutation (Δ536) completely abolished the PKC activation-mediated degradation of Kv1.5 channels. These results provide mechanistic insight into PKC activation-mediated Kv1.5 degradation.

#WhatWouldYouDo? A cross-sectional study of sports medicine physicians assessing their competency in managing harassment and abuse in sports.

OBJECTIVES: To assess the clinical competence of sports medicine physicians to recognise and report harassment and abuse in sports, and to identify barriers to reporting and the need for safeguarding education. METHODS: We implemented a cross-sectional cohort study design recruiting through social media and international sports medicine networks in 2023. The survey captured participant perceptions related to the harmfulness of harassment and abuse. The survey incorporated the reasoned action approach as a theoretical framework to design survey questions to identify attitudes and self-efficacy to detect and report suspicions of harassment and abuse and to identify barriers to reporting. RESULTS: Sports medicine physicians (n=406) from 115 countries completed the survey. The situations of harassment and abuse presented in the survey were described by sports medicine physicians as having occurred in the 12 months before participating in the survey. Despite recognising the situations as harmful, sports medicine physicians were somewhat uncomfortable being vigilant for the signs and symptoms and reporting suspicions and disclosures of harassment and abuse (M=2.13, SD=0.67). In addition, just over one-quarter (n=101, 26.9%) was unaware of where to report harassment and abuse, and over half did not know (n=114, 28.1%), or were uncertain (n=95, 23.4%) of who the safeguarding officer was in their sports organisation. Participants identified many barriers to reporting harassment and abuse, including concerns regarding confidentiality, misdiagnosis, fear of reprisals, time constraints and lack of knowledge. Over half felt insufficiently trained (n=223, 57.6%), and most respondents (n=324, 84.6%) desired more education in the field. CONCLUSIONS: Educational programmes to better recognise and report harassment and abuse in sports are needed for sports medicine trainees and practising clinicians. An international safeguarding code for sports medicine physicians should be developed.

The Safety and Feasibility of Ambulatory Minimally-Invasive Partial Nephrectomy: A Systematic Review and Meta-Analysis.

PURPOSE: Emerging evidence supports the use of minimally invasive partial nephrectomy (MIPN) in ambulatory settings. We conducted a systematic review and meta-analysis to evaluate differences in perioperative characteristics, complication/readmission rates and satisfaction/cost data between ambulatory and standard-length discharge (SLD) MIPN. METHODS: This study was prospectively registered in PROSPERO (CRD42023429854). A systematic literature search of PubMed, Embase, and Web of Science databases was conducted, including studies comparing ambulatory MIPN versus SLD MIPN for patients with renal masses. Studies were assessed for quality using the Methodological Index for Non-Randomized Studies score. Meta-analysis was performed for comparative studies, and non-comparative studies were included narratively. RESULTS: Eleven studies were included with a pooled population of 20,575 patients, of which 1,419 (7%) had a length of stay less than 1 day and were considered the ambulatory group. There were no significant differences in the total complication rates (RR: 0.50, 95% CI: 0.24, 1.04; p = 0.06) or 30-day readmission rates (RR: 0.87, 95% CI: 0.56, 1.35; p=0.53) between the ambulatory and SLD groups. There were fewer > 3 Clavien-Dindo complications in the ambulatory group (RR: 0.34, 95% CI: 0.19, 0.59; p = 0.0002). Few studies reported average healthcare cost and patient satisfaction. CONCLUSIONS: In appropriately selected patients, ambulatory MIPN is safe and feasible. Future studies are needed to quantify cost and patient satisfaction differences and further identify appropriate patient selection criteria for ambulatory MIPN. SOURCES OF FUNDING: No funding.

Serum total testosterone is associated with phosphate and calcium excretion in response to oral phosphate loading in healthy middle-aged males.

Androgen receptors are expressed in the kidney and serum testosterone is negatively associated with serum phosphate in males, suggesting a role of testosterone in renal phosphate handling. In this cross-sectional study, we examined the association of serum total and free testosterone with acute phosphate and calcium excretion in males in response to an oral phosphate challenge. Thirty-five healthy adult males with normal baseline testosterone levels consumed a 500 mg phosphorus drink and the urinary excretion of minerals, as well as levels of relevant circulating parameters, were assessed at baseline and hourly for 4 h. Serum total testosterone was positively associated with overall phosphate excretion (r = 0.35, p = 0.04) and calcium excretion (r = 0.44, p = 0.00) in response to the challenge. Serum free testosterone was positively associated with post-challenge calcium excretion (r = 0.34, p = 0.048), but significance was not reached for phosphate excretion (r = 0.31, p = 0.07). Serum total and free testosterone were not associated with parathyroid hormone, fibroblast growth factor-23, or vitamin D-key factors implicated in phosphate and calcium regulation. Overall, higher serum total testosterone levels in healthy middle-aged males are associated with a greater capacity to acutely excrete phosphate and calcium after a single oral phosphate challenge, suggesting potential ramifications of testosterone deficiency related to mineral homeostasis.

Sex Differences in Phosphate Homeostasis: Females Excrete More Phosphate and Calcium After an Oral Phosphate Challenge.

CONTEXT: Dietary consumption of phosphate is increasing, and elevated serum phosphate is associated with increased cardiovascular disease (CVD) risk. Sex differences in phosphate homeostasis and response to changes in dietary phosphate intake, which are not captured by clinically measured analytes, may contribute to differences in CVD presentation and bone disease. OBJECTIVE: To assess sex differences in acute phosphate homeostasis in response to a single oral phosphate challenge. DESIGN: Cross-sectional. SETTING: General community. PARTICIPANTS: 78 participants (40-76 years) with measured glomerular filtration rate >60 mL/min/1.73 m2 and no clinically diagnosed CVD and 14 young healthy adults. MAIN OUTCOME MEASURES: To elucidate subtle alterations in phosphate homeostasis, we employ an acute challenge whereby the hormonal response, circulating mineral levels, and urinary excretion are assessed following an oral challenge of phosphate. RESULTS: Although both males and females had similar changes in circulating phosphate, calcium, and parathyroid hormone in response to the challenge, females excreted ∼1.9x more phosphate and ∼2.7x more calcium than males, despite not consuming calcium. These sex differences were recapitulated in healthy young adults. This excretion response did not correlate to age, serum phosphate, or estradiol levels. The females with greater excretion of phosphate had higher levels of bone resorption markers compared to formation markers. CONCLUSIONS: Taken together, these data identify sex differences in acute phosphate homeostasis, specifically that females may mobilize and excrete endogenous sources of calcium and phosphate in response to oral phosphate compared to males. While high levels of dietary phosphate negatively impact bone, our results suggest that females may incur more risk from these diets.