Faculty - Pamela L. Tuma

Pamela L. Tuma Associate Professor

Room: Nursing-Biology 260A Phone: 202-319-6681 Fax: 202-319-5721 e-mail: tuma@cua.edu

EDUCATION AND TRAINING :

BS, Cell Biology, University of Kansas, Lawrence, KS

BA, Communications Studies, University of Kansas, Lawrence, KS

PhD, Cell, Molecular and Structural Biology, Northwestern University School of Medicine, Chicago, IL

Postdoctoral Research, Polarized membrane trafficking, Johns Hopkins University School of Medicine, Baltimore, MD

TEACHING INTERESTS:

Biochemistry Biochemistry Laboratory Membrane Trafficking and Human Disease Signal Transduction and Biomembranes

RESEARCH INTERESTS:

The work in the Tuma lab is divided into two major areas.  The first area examines how the exquisite architecture of the hepatocyte (the major liver cell type) is reflected in its cellular function (Part 1).  Our second area of research is newer to the lab and is a collaborative effort with the University of Nebraska Medical Center (Omaha, NE).  Together, we have developed a new strategy to examine the liver damage associated with alcoholic liver disease.  We have determined that a polarized hepatic cell line, the WIF-B cells, is an excellent system to study alcohol-induced liver damage and are working to understand how liver cell structure and thus, function is altered by chronic alcohol consumption (Part 2). 

Part 1.  Understanding normal liver cell structure and function

What is the relationship between liver cell structure and function?  The liver, the body’s largest organ, performs many vital functions.  It converts food into chemicals required for life, it makes numerous compounds used throughout the body, and it detoxifies and rids the body of poisonous substances (e.g., see Part 2). The proper performance of the hepatocyte relies on its specific cellular architecture, a combination of its structure and function. These cells form a barrier between the internal and external liver environments by bonding themselves together with specialized structures called tight junctions. These junctions in turn divide the cell surface into two domains: the basolateral and apical.  The basolateral cell surface faces the blood that flows through the liver (the internal environment) whereas the apical surface faces the bile (the external environment), the complex molecular “soap” stored in the gallbladder that helps us absorb dietary fats and remove waste products.  Because these two surfaces are in contact with vastly different environments, they each perform specific tasks.  For example, the basolateral surface communicates with the blood either by releasing compounds the liver has made for delivery to other organs, or by retrieving compounds from the blood for the liver’s use or detoxification. The apical surface similarly “communicates” with the bile by releasing substances destined for excretion.  To perform these surface-specific tasks, the basolateral and apical domains have their own unique set of molecular machinery. How is this machinery specifically delivered to its proper cellular home? This is the fundamental question my research addresses.

The role of MAL proteins in regulating apical delivery.  Our long-term goal is to understand how hepatic cells establish and maintain their polarity. Our focus is to identify regulators of apical plasma membrane (PM) delivery. Unlike simple epithelial cells that directly target proteins from the TGN to the apical PM, hepatocytes use an indirect pathway: proteins are first delivered to the basolateral domain, then selectively internalized and transcytosed to the apical surface. MAL and MAL2 have been identified as regulators of direct and indirect apical delivery, respectively.  We have previously shown that indirect sorting in hepatocytes requires cholesterol and glycosphingolipids.  Because MAL and MAL2 have been identified as important regulators of apical PM delivery in both pathways and because their activity requires cholesterol and glycosphingolipids, we have been examining how MAL proteolipids function in apical PM sorting in polarized hepatic cells.

Part 2.  Alterations in liver structure and function associated with alcoholic liver disease

Why study alcoholic liver disease? Approximately 75% of all Americans consume alcohol, and 100,000 deaths per year are attributed to alcohol consumption.  Of those deaths, more than 20,000 are caused by liver cirrhosis, the seventh largest cause of death among Americans.  Although alcoholic liver disease is a major biomedical health concern in the United States, little is known about how alcohol induces liver injury.  Defining how alcohol consumption changes liver cell structure and function is critical for the development of effective treatments for patients suffering not only from alcoholic liver disease, but also from other liver diseases (e.g., hepatitis, liver cancer) that lead to cirrhosis. 

Why study alcohol-induced liver damage in WIF-B cells? The liver is the major site of alcohol metabolism, and thus, the most susceptible organ to alcohol-induced injury.  In the early stages of the disease, a fatty liver develops which can lead to hepatocyte injury, liver fibrosis, and ultimately to cirrhosis.  Although the disease progression is well described in patients, it is not understood why and how this progression occurs. Traditionally, animal models (e.g., rats, primates) have been used to describe physiological responses to alcohol consumption, but these approaches can be problematic.  Animals can vary significantly in their responses to alcohol, and it is often difficult and expensive to do animal studies.  Thus, many researchers are trying to find alternative strategies to study alcohol-induced liver damage.  We have been developing one such alternative strategy: WIF-B cells.  These cells maintain their liver-specific structure and functions in vitro and efficiently metabolize alcohol like intact liver. Also importantly, they exhibit the same cellular alterations as seen in alcohol-exposed livers.  We are examining the effects of alcohol exposure on membrane trafficking with respect to alcohol-induced alterations in microtubule modifications and dynamics. 

RESEARCH FUNDING:

Dr. Tuma is funded by an R15 Academic Research Enhancement Award from the National Institutes of Health, National Institute of General Medical Sciences and an R21 Exploratory/Developmental Research Award from the National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism.

RECENT PUBLICATIONS:

Shepard, B.D., and P.L. Tuma. 2009. Alcohol-induced protein hyperacetylation: mechanisms and consequences. World J Gastroenterol. 15:1219-1230.

Shepard, B.D., Joseph, R.A., Kannarkat, G.T., Rutledge, T., Tuma, D.J., and P.L. Tuma. 2008. Ethanol induced alterations in hepatic microtubule dynamics may be explained by impaired function of the microtubule deacetylase, HDAC6. Hepatology. 48:1671-1679.   

Ramnarayanan, S.P., In, J.G., Shepard, B.D., and P.L.Tuma. 2008. Immunoblots. In: Biological Research Methodology - A Handbook. F. Casorta and J.J. Greene, Editors. Taylor and Francis Group, Publishers. Florence, KY (in press).

In, J.G., Shepard, B.D., Ramnarayanan, S.P., and P.L.Tuma. 2008.  Immunoprecipitations. In: Biological Research Methodology - A Handbook. F. Casorta and J.J. Greene, Editors. Taylor and Francis Group, Publishers. Florence, KY (in press).

Joseph, R. A., Shepard, B.D., Kannarkat, G.T., Rutledge, T., Tuma, D.J., and P.L. Tuma. 2008. Microtubule acetylation and stability may explain alcohol-induced alterations in hepatic protein trafficking. Hepatology. 47:1745-53.

Ramnarayanan, S.P., Cheng, C.A., Bastaki, M., and P.L. Tuma. 2007. Exogenous MAL selectively reroutes apical delivery in polarized, hepatic WIF-B cells. Molec. Biol. Cell. 18:2707-15.

McVicker, BL., Tuma, DJ., Kubik, JA., Tuma, PL, and CA Casey. 2006. Ethanol-induced apoptosis in polarized hepatic cells.  Alcoholism: Clin Exp Res 30:1906-15

Kannarkat, G.T., Tuma, D.J., and P.L. Tuma. 2006.  Microtubules are more stable and more highly acetylated in ethanol-treated hepatic cell. J. Hepatol. 44:963-970.

Hanson, L., May, L., Ambudkar, S.V., Tuma, P.L., Keeven, J., Mehl, P., and J. Golin. 2005.  The role of hydrogen bond-acceptor groups in the interaction of substrates with Pdr5p, a major yeast drug transporter.  Biochemistry 44:9703-9713.

Shaffert, C.S., Todero, S.L., McVicker, B.L., Tuma, P.L., Sorrell, M.F. and D.J. Tuma. 2004.  WIF-B cells as a model for studying aclcohol-induced hepatocyte injury.  Biochem.  Pharmacol.  67:2167-2174. 

Graf, G.A., Yu, L., Li, W.P., Gerard, R., Tuma, P.L., Cohen, J. and H.H. Hobbs.  2003.  ABCG5 and ABCG8 are obligate heterodimers for protein trafficking and biliary cholesterol excretion.  J. Biol. Chem.  278:48275-48282.

Nyasae, L.K., Hubbard, A.L. and P.L. Tuma. 2003. Transcytotic efflux from early endosomes is dependent on cholesterol and glycosphingolipids in polarized hepatocytes. Molec. Biol. Cell 14:2689-2705.

Tuma, P.L. and A.L. Hubbard. 2003. Transcytosis: Crossing cellular barriers. Physiological Reviews 83:871-932.

Tuma, P.L., Nyasae, L.K., and A.L. Hubbard. 2002. Nonpolarized cells selectively sort apical proteins from the cell surface to a novel compartment, but lack apical retention mechanisms. Molec. Biol. Cell 13:3400-3415

Tuma, P.L., Nyasae, L.K., Backer, J.M., and A.L. Hubbard. 2001. Vps34p differentially regulates endocytosis from the apical and basolateral domains in polarized hepatic cells. J. Cell Biol. 154: 1197-1208.

Tuma, P.L., and A.L. Hubbard. 2001. The hepatocyte surface: dynamic polarity. In: Liver Biology and Pathobiology. I.M. Arias, J.L. Boyer, F.V Chisari, N. Faust, D. Schachter and D.A. Shafritz, editors. Raven Press, New York, NY. 97-117.

Tuma, P.L., and A.L. Hubbard. 1999. Isolation of rat hepatocyte plasma membrane sheets and plasma membrane domains. Supplement. In: Current Protocols in Cell Biology. J.S. Bonifacino, M. Dasso, J. Lippincott Schwartz, J.B. Harford and K.M. Yamada, editors. John Wiley and Sons, New York, NY. 3.2.1-16.

Lapierre, L.A., Tuma. P.L., Navarre, J., Goldenring, J.R., and J.M. Anderson. 1999. VAP-33 localizes to both an intracellular vesicle population and with occludin at the tight junction. J. Cell Sci. 112: 3723-3732.

Tuma, P.L., Finnegan, C.M., Yi, J.-H., and A.L. Hubbard. 1999. Evidence for apical endocytosis in hepatic cells: resident apical plasma membrane proteins redistribute into lysosomally-derived vacuoles in the presence of phosphoinositide 3-kinase inhibitors. J. Cell Biol. 145:1089-1102.

*Fujita, H., *Tuma, P.L., Finnegan, C.M., Locco, L. and A.L. Hubbard. 1998. Endogenous syntaxins 2, 3 and 4 exhibit distinct but overlapping patterns of expression at the hepatocyte plasma membrane. Biochem. J. 329:527-538. *contributed equally

Tuma, P.L., and C.A. Collins. 1995. Dynamin forms polymeric complexes in the presence of lipid vesicles: characterization of chemically cross-linked dynamin molecules. J. Biol. Chem. 270:26707-26714.

Tuma, P.L., and C.A. Collins. 1994. Activation of dynamin GTPase is a result of positive cooperativity. J. Biol. Chem. 269:30842-30847.

Tuma, P.L., Stachniak, M.C., and C.A. Collins. 1993. Activation of dynamin GTPase by acidic phospholipids and endogenous rat brain vesicles. J. Biol. Chem. 268:17240-17246.