The goal of my current work is to examine how ethanol exposure results in impaired function of the Golgi apparatus. The Golgi apparatus (also called the Golgi body or Golgi complex) packages proteins into membrane bound vesicles inside the cell before the vesicles are sent to their destination. As such, this organelle resides at the intersection of the secretory, lysosomal, and endocytic pathways; it is known to be of particular importance in processing proteins for secretion. Previous work from our laboratory has identified multiple defects in endocytosis, protein trafficking, and secretion, after alcohol administration, but we have not until now, examined a role for altered Golgi function in these processes. Because the incidence of alcoholic liver disease is greater in the Veteran population and more than half of all medical admissions in VA Medical Centers across the country are linked to alcohol abuse, we are focusing efforts towards the identification of potential targets to intervene during the progressive injury which occurs after chronic alcohol administration, and perhaps the Golgi will prove to be such a target. Of central importance to our study is the role of a small GTPase, Rab3D, which is involved in exocytosis, secretion and vesicle trafficking. We have shown that Rab3D protein content was significantly decreased after alcohol administration, and recently we have obtained exciting new preliminary data that ethanol- impaired Rab3D function plays an important role in Golgi disorganization and fragmentation. The studies proposed in this application will extend our ongoing investigation of how ethanol alters hepatocyte biology, specifically in protein processing, to an examination of its role in transport through the Golgi. We provide a concept as to how alcohol-induced remodeling of Golgi morphology is a significant impairment of post-Golgi trafficking, and this leads to utilization of trans-Golgi membranes for the formation of autophagosomes. For this work, we present the following hypothesis: Ethanol exposure contributes to Golgi disorganization via its fragmentation and autophagy-mediated Golgi membrane lysis, leading to impaired endocytic and exocytic protein trafficking. Altered distribution and function of the small GTPase Rab3D plays a critical role in these alterations. To examine our hypothesis, we have proposed three specific aims;
in Aim 1 we will characterize the distribution of Rab3D in vitro and in vivo in liver cells before and after EtOH administration. Studies proposed for Aim 2 will establish a role for Rab3D in the transport of physiologically relevant hepatic proteins. These studies will be followed by experiments proposed for Aim 3 where we will determine if EtOH- induced Golgi disorganization and fragmentation contribute to autophagosome formation and how altered Rab3D function affects hepatocyte autophagy. Altogether, successful completion of these aims will characterize the effect of EtOH on Golgi disorganization, and establish a role for altered Rab3D during this process. We will be able to correlate mechanisms of alcohol-mediated liver cell trafficking impairments with impaired Golgi function and provide key information that could lead to therapeutic strategies aimed at reducing or eliminating liver injury. In this work, I am joined by three outstanding co-investigators (Drs. Petrosyan, Thomes and Rasineni), the latter two are young investigators based at the Omaha VA. I also have collaborative effort with multiple VA investigators, as outlined in my research plan, and these collaborations have been highly productive. The exploration of how alcohol impairs function of important organelles such as the Golgi and lipid droplets will provide new avenues for the development of therapeutic interventions for both alcoholic and non-alcoholic fatty liver disease. Our contribution is significant since this is a critical step to provide translational knowledge for the development of therapies for fatty liver disease. Additionally, our findings will also have broader implications for other hepatic diseases characterized by hepatic injury. With the expertise and collaborations available to my group, we anticipate that we will be successful in these studies and will be able to contribute to improved healthcare for Veteran patients by the identification of mechanisms involved in the alcoholic liver injury.
This proposal addresses a significant healthcare issue that affects Veterans, military personnel, and their families disproportionately to the general population. Here, work from Dr. Casey?s research program is focused on the investigation of alcoholic and non-alcoholic fatty liver disease (AFLD and NAFLD, respectively). Both AFLD and NAFLD represent a major clinical challenge in the VA, since there are no current, effective therapeutic interventions, and progression of liver injury can result in liver transplantation, or death. Work from our lab aims to provide a better understanding of AFLD and NAFLD progression and to increase opportunities for the development of novel treatment paradigms for the management of chronic liver diseases.
