For the liver to function normally, the hepatocytes must interact concurrently with blood, bile and other hepatocytes via the three structurally and functionally distinguishable domains of their plasma membranes (sinusoidal, bile canalicular and lateral, respectively). During liver regeneration, hepatocytes undergo cell division without any permanent disruption of liver function. I propose to use the regenerating rat liver system to study hepatocyte surface structure and function during mitosis in situ, with special attention to the behavior of those integral membrane receptors, enzymes and protein antigens known to be localized to a particular plasmalemmal domain on the nonproliferating rat hepatocyte (the """"""""domain markers""""""""). Antibody and/or ligand reagents for a number of the domain markers are already at my disposal. Having first examined the surface ultrastructure of mitotic hepatocytes by electron microscopy, I will: (1) quantify domain markers in hepatocyte plasma membrane fractions isolated from regenerating livers, (2) morphologically assess the endocytic function of doman-specific surface receptors on mitotic hepatocytes using cytochemical tracers and (3) localize domain markers on mitotic hepatocytes by immunocytochemical and cytochemical means. These experiments will determine the extent to which normal hepatocyte plasma membrane domain structure is maintained during mitosis and is intended to reveal the mechanism by which plaasma membrane polarity is conveyed to daughter hepatocytes during cell division. In addition, I will utilize a combination of monoclonal antibody technology and conventional biochemistry to identify mitosis-specific proteins of the rat hepatocyte plasma membrane. Any such components will be selected for further study because of the likelihood that they perform important structural or functional roles during mitosis. Virtually all of the techniques to be cultivated in this project are readily applicable to the study of the hepatocyte surface alterations associated with normal development and certain disease states, including hepatocarcinoma, cirrhosis, cholestasis, and hepatitis.
| Hubbard, A L; Stieger, B; Bartles, J R (1989) Biogenesis of endogenous plasma membrane proteins in epithelial cells. Annu Rev Physiol 51:755-70 |
| Bartles, J R; Feracci, H M; Stieger, B et al. (1987) Biogenesis of the rat hepatocyte plasma membrane in vivo: comparison of the pathways taken by apical and basolateral proteins using subcellular fractionation. J Cell Biol 105:1241-51 |
