PROJECT SUMMARYCopper (Cu) is an essential transition metal regulated by a complex set of transporters and chaperones.Mammals rely on two related p-type ATPases, ATP7A and ATP7B, to regulate intracellular Cu levels andcoordinate its intestinal absorption and biliary excretion. Depending on Cu availability, ATP7A and ATP7B areactively trafficked from trans-Golgi network (TGN) to cytosolic vesicles to mediate extracellular Cu excretion. Atthe organismal level, ATP7A plays a required role in intestinal Cu absorption while of ATP7B is required forbiliary excretion. COMMD1, the founding member of a highly conserved family that includes 9 additionalmembers, has been long known to play a role in mammalian Cu metabolism.Recent work from ourlaboratories has uncovered that COMMD1 regulates the endosomal sorting of ATP7A.This is mediatedthrough the formation of a complex containing CCDC22 and its homologous protein, CCDC93, termed theCOMMD/CCDC22/ CCDC93 or CCC complex. The CCC complex can exist in alternative configurationsdepending on the recruitment of specific COMMD proteins. COMMD1-CCC binds to the WASHcomplex, acritical regulator of receptor trafficking withinthe endo-lysosomal system. WASH activates the Arp2/3 complex,leading to branched F-actin deposition on endosomes, a required step for the generation of transport vesiclescontaining recycling cargo proteins such as ATP7A. In contrast, we recently reported that COMMD9-CCCplays an essential role in the endosomal recycling of other proteins, such as Notch. Emerging data indicatesthat COMMD9 also participates in ATP7A trafficking. However, it remains unclear how the CCC complexregulates endosomal sorting and in which way do different COMMD-containing CCC complexes collaborate inthis process. The overall goal of this project is to provide a deep mechanistic understanding for the role ofCOMMD proteins in endosomal sorting and their impact in Cu homeostasis. Our hypothesis is that theprimary function of the CCC complex is to regulate WASH activity. Furthermore, we hypothesize that differentCOMMD proteins function to localize the CCC complex to different endosomal sub-compartments to mediatecargo-specific effects and/or to regulate WASH activity along a continuum of sorting steps. The followingspecific aims will be pursued: (1) To uncover the mechanism by which the CCC complex regulates WASHactivity. Here we will examine how CCC regulates F-Actin deposition on endosomes. (2) To understand thecontribution of the COMMD9-CCC complex in endosomal trafficking. Here we will examine mechanisticallyhow COMMD9 adds to the sorting process. (3) To assess the role of COMMD9 in cu homeostasis at theorganismal level. Here we will use tissue specific Commd9 knockout mice to study the role of this gene in Cumetabolism in vivo. Altogether, the proposed studies will uncover critical aspects of vesicular sorting that havewide ranging implications in biology and human disease, as well as examine these pathways and their impacton Cu homeostasis.
|Effective start/end date||8/1/16 → 5/31/21|
- National Institutes of Health: $447,535.00