The long-term goal ofthe grant is to understand how the processing and trafficking of CFTR to the plasma membrane Is regulated. CFTR Is a protein that in several epithelia such as the airway functions at the apical cell membrane. We have shown previously that the trafficking of CFTR from the Golgi to the plasma membrane is regulated by three proteins, the PDZ domain containing protein, CAL, the small molecular weight GTPase, TC10, and the SNARE protein, STX6, which we now refer to as the CALcomplex. The present proposal posits that In addition to its role in regulating the surface expression of CFTR, CAL also plays a role In regulating the amount of immature CFTR protein by interacting with proteins in the cell's quality control mechanism which includes ER processing of newly synthesized proteins followed by proteasomal and aggresomal degradation of incorrectly folded proteins. A process termed ERAD. To study this further we propose to address the following: 1. What is the physiological role ofthe CAL-complex in the processing the Immature wt- and A508-CFTR? Precisely how is the processing of immature CFTR by the ER regulated by the TC10-GTP/GDP cycle and bySTXe? 2. What is the physiological role ofthe CAL-complex in the regulation of rescued A508-CFTR at the cell surface? And precisely how is the trafficking of rescued A508-CFTR to the plasma membrane regulated by TCI 0-GTP/GDP cycle? 3. Does the CAL complex interact with key proteins in the ER quality control mechanism? All of these studies will employ a combination of approaches that will strength the overall Program Project Grant. Likewise, the proposal will gain expertise and collaboration from members of the PPG that will enhance the likelihood of success beyond what could be achieved as an individual stand alone application. The ultimate goal is to provide novel insights into physiological process regarding how CFTR functions in a macromolecular complex In polarized epithelial tissues.
The experiments described within this proposal represent a new area of Investigation with implications for our understanding of A508-CFTR processing and trafficking. Identification ofthe critical pathways and establishment of their roles will pave the way for the development of drugs to therapeutically alter the switching mechanisms that determine A508-CFTR's fate in Cystic Fibrosis.
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