Cell Biology of Human Vit C Transporters in Liver Cells

这项研究职业发展计划的主要目的是让首席研究员学习

The main purpose of this research career development plan is to allow the Principle Investigator to learn recent advances in imaging and molecular biology techniques, boosting his career goal to become an independent academic investigator in the area of cell biology with an emphasis on the intracellular traficking and membrane targeting of different transporters in epithelial and non-epithelial cellular systems relating the work to human health and disease. Ascorbic acid (vitamin C) is an essential micronutrient required for normal human health and well being. Recently two isoforms of the human sodium-dependent vitamin C transporters (hSVCTI and hSVCT2) have been cloned and their abundant expression has been reported in human liver and other tissues. Nothing is known about the mechanisms that dictate the hSVCTI and hSVCT2 targeting to the human liver hepatocyte cell surface. Membrane targeting and polarized expression of membrane transporters is not only important in order to establish polarity in epithelial cells, but is also vital when studying regulation via insertion/retrival of membrane transporters. Further, recent studies have shown that impairment in a transport event could be mediated via defective trafficking/mis-targeting of the transport carriers to the cell membrane. Therefore, research on the membrane targeting and intracellular trafficking of transport carriers is important from cell biology/physiology standpoints. Targeting of a protein to the plasma membrane has been shown to involve specific targeting signals such as tyrosine, di-leucine, di-acidic, di- basic, proline rich and PDZ domains embedded in the polypeptide. Using HepG2 and Wif-B9 cells as models, our specific aims are:1) To identify the molecular mechanisms that mediate the targeting of the hSVCTI and hSVCT2 proteins to the plasma membrane by employing confocal imaging, 2) Determine what role the microtubule network and the actin microfilaments play in intracellular trafficking of hSVCTI and hSVCT2, investigate if these trafficking events involve vesicles and motor proteins, and if they are regulated by specific protein kinase-mediated pathways. A combination of cell/biochemical/molecular biological and imaging methods will be used in these investigations. The research described in this proposal will not only enable the applicant to achieve his career goals, but will also contribute to a better understanding of the cell biology and regulation of vitamin C transporters in particular, and transporters of other nutrients in general.