Modelling of Double Hit Mutations in Thoracic Aortic Aneurysm Disease that have Variable Impact on Phenotype

Abstract

mutants with either wild type TRPML3 or a non-functional ER-retained mutant, TRPML3-KK, we examined how differentially targeted TRPML1 proteins affect TRPML3 localization. We show that while the wild type TRPML1 decreased the PM targeting of TRPML3, the PM-targeted TRPML1 mutants did not enhance PM localization of TRPML3. Interestingly, not only the wild type TRPML1 brought TRPML3-KK to lysosomes, but also TRPML3 brought the ER-retained TRPML1-KK to these acidic organelles. Moreover, coexpression of TRPML-KK not only reduced TRPML3-mediated Ca 2þ response to a TRPML agonist, but also nearly abolished PM localization of TRPML3. We conclude that while the lysosome targeting sequence(s) is important for sorting TRPML channels out of ER-Golgi network, the ion-conducting function may be critical for PM trafficking of these endolysosomal channels.