Robichaud, Jielu Hao

Tuberous sclerosis complex (TSC) is a highly variable autosomal dominant disease characterized by dysregulated organ development and growth. Benign tumors, termed hamartomas, may occur across organ systems but typically involve the kidney, brain, skin, heart, and lung. The diagnosis, surveillance, and clinical management of TSC requires a multidisciplinary approach, adopted by dedicated multispecialty centers worldwide. Nephrology involvement predominantly stems from the morbidity and mortality related to the prototypical kidney lesion, angiomyolipomas, whose presence and degree confers risk of CKD, hypertension, retroperitoneal bleeding, and possibly renal cell carcinoma. Surveillance of kidney structural lesions, kidney function, and BP may enable early interventions that limit kidney-related morbidity and mortality, such as mammalian target of rapamycin inhibitor therapy. We review the epidemiology, genetics, and pathogenesis of TSC and how these inform the evaluation, diagnosis, and clinical management of TSC from the vantage point of the treating nephrologist.

Tubulin polyglutamylation is a posttranslational modification that occurs primarily along the axoneme of cilia. Defective axoneme polyglutamylation impairs cilia function and has been correlated with ciliopathies, including Joubert Syndrome (JBTS). However, the precise mechanisms regulating proper axoneme polyglutamylation remain vague. Here, we show that cyclin-dependent kinase 6 (CDK6), but not its paralog CDK4, localizes to the cilia base and suppresses axoneme polyglutamylation by phosphorylating RAB11 family interacting protein 5 (FIP5) at site S641, a critical regulator of cilia import of glutamylases. S641 phosphorylation disrupts the ciliary recruitment of FIP5 and its association with RAB11, thereby reducing the ciliary import of glutamylases. Encouragingly, the FDA-approved CDK4/6 inhibitor Abemaciclib can effectively restore cilia function in JBTS cells with defective glutamylation. In summary, our study elucidates the regulatory mechanisms governing axoneme polyglutamylation and suggests that developing CDK6-specific inhibitors could be a promising therapeutic strategy to enhance cilia function in ciliopathy patients.

AbstractCisplatin nephrotoxicity has been considered as serious side effect caused by cisplatin‐based chemotherapy. Recent evidence indicates that renal tubular cell apoptosis and inflammation contribute to the progression of cisplatin‐induced acute kidney injury (AKI). Hepatocyte nuclear factor 1β (HNF1β) has been reported to regulate the development of kidney cystogenesis, diabetic nephrotoxicity, etc However, the regulatory mechanism of HNF1β in cisplatin nephrotoxicity is largely unknown. In the present study, we examined the effects of HNF1β deficiency on the development of cisplatin‐induced AKI in vitro and in vivo. HNF1β down‐regulation exacerbated cisplatin‐induced RPTC apoptosis by indirectly inducing NF‐κB p65 phosphorylation and nuclear translocation. HNF1β knockdown C57BL/6 mice were constructed by injecting intravenously with HNF1β‐interfering shRNA and PEI. The HNF1β scramble and knockdown mice were treated with 30 mg/kg cisplatin for 3 days to induce acute kidney injury. Cisplatin treatment caused increased caspase 3 cleavage and p65 phosphorylation, elevated serum urea nitrogen and creatinine, and obvious histological damage of kidney such as fractured tubules in control mice, which were enhanced in HNF1β knockdown mice. These results suggest that HNF1β may ameliorate cisplatin nephrotoxicity in vitro and in vivo, probably through regulating NF‐κB signalling pathway.