METHODS: We performed electrophysiologic, biochemical, and biophysical experiments to elucidate the molecular mechanism underlying calmodulin (CaM)-mediated Ca2+-dependent inactivation (CDI) of TRPC6. To address the pathophysiologic contribution of CDI, we assessed the actin filament organization in cultured mouse podocytes.
RESULTS: Both lobes of CaM helped induce CDI. Moreover, CaM binding to the TRPC6 CaM-binding domain (CBD) was Ca2+-dependent and exhibited a 1:2 (CaM/CBD) stoichiometry. The TRPC6 coiled-coil assembly, which brought two CBDs into adequate proximity, was essential for CDI. Deletion of the coiled-coil slowed CDI of TRPC6, indicating that the coiled-coil assembly configures both lobes of CaM binding on two CBDs to induce normal CDI. The FSGS-associated TRPC6 mutations within the coiled-coil severely delayed CDI and often increased TRPC6 current amplitudes. In cultured mouse podocytes, FSGS-associated channels and CaM mutations led to sustained Ca2+ elevations and a disorganized cytoskeleton.
CONCLUSIONS: The gain-of-function mechanism found in FSGS-causing mutations in TRPC6 can be explained by impairments of the CDI, caused by disruptions of TRPC's coiled-coil assembly which is essential for CaM binding. The resulting excess Ca2+ may contribute to structural damage in the podocytes.
METHODS: We compared 2 different consecutive video libraries (40 video per arm) collected at Humanitas Research Hospital with 2 different CADe system brands (CADe A and CADe B). For each video, the number of CADe false activations, the cause and the time spent by the endoscopist to examine the area erroneously highlighted were reported. The FP activations were classified according to the previously developed classification of false positives (the NOISE classification) according to their cause and relevance.
RESULTS: A total of 1021 FP activations were registered across the 40 videos of the Group A (25.5±12.2 FPs per colonoscopy). A comparable number of FPs were identified in the Group B (n=1028, mean:25.7±13.2 FPs per colonoscopy) (p 0.53). Among them, 22.9±9.9 (89.8%, Group A), and 22.1±10.0 (86.0%, Group B) were due to artifacts from bowel wall. Conversely, 2.6±1.9 (10.2%) and 3.5±2.1 (14%) were caused by bowel content (p 0.45). Within the Group A each false activation required 0.2±0.9 seconds, with 1.6±1.0 (6.3%) FPs requiring additional time for endoscopic assessment. Comparable results were reported within the Group B with 0.2±0.8 seconds spent per false activation and 1.8±1.2 FPs per colonoscopy requiring additional inspection.
CONCLUSION: The use of a standardized nomenclature permitted to provide comparable results with either of the 2 recently approved CADe systems.