A molecular mechanism underlying genotype-specific intrahepatic cholestasis resulting from MYO5B mutationsOvereem, A. W., Li, Q., Qiu, Y-L., Carton-Garciá, F., Leng, C., Klappe, K., Dronkers, J., Hsiao, N-H., Wang, J-S., Arango, D. & van IJzendoorn, S. C. D., 21-Nov-2019, In : Hepatology.
Research output: Contribution to journal › Article › Academic › peer-review
BACKGROUND AND RATIONALE FOR THE STUDY: Progressive familial intrahepatic cholestasis (PFIC)6 has been associated with missense but not biallelic nonsense or frameshift mutations in MYO5B, encoding the motor protein myoVb. This genotype-phenotype correlation and the mechanism via which MYO5B mutations give rise to PFIC are not understood. The aim of this study was to determine whether the loss of myoVb or expression of patient-specific myoVb mutants can be causally related to defects in canalicular protein localization and, if so, via which mechanism.
MAIN RESULTS: We demonstrate that the cholestasis-associated P660L mutation in myoVb caused the intracellular accumulation of bile canalicular proteins in vesicular compartments. Remarkably, the knockout of MYO5B in vitro and in vivo produced no canalicular localization defects. In contrast, the expression of myoVb mutants consisting of only the tail domain phenocopied the effects of the Myo5b-P660L mutation. Using additional myoVb and rab11a mutants, we demonstrate that motor domain-deficient myoVb inhibited the formation of specialized apical recycling endosomes, and that its disrupting effect on the localization of canalicular proteins was dependent on its interaction with active rab11a and occurred at the trans-Golgi Network/recycling endosome interface.
CONCLUSIONS: Our results reveal a mechanism via which MYO5B motor domain mutations can cause the mislocalization of canalicular proteins in hepatocytes which, unexpectedly, does not involve myoVb loss-of-function but, as we propose, a rab11a-mediated gain-of-toxic function. The results explain why biallelic MYO5B mutations that affect the motor domain but not those that eliminate myoVb expression are associated with PFIC6.
|Publication status||E-pub ahead of print - 21-Nov-2019|