R. Brian Doctor, Ph.D. (PI)
Evgenia Dobrinskikh, Ph.D.
DeeAnn Cranston, Ph.D.
Our laboratory seeks to understand the physiology and pathophysiology of the epithelial cells that line the intrahepatic bile duct. These cells, termed cholangiocytes, have a potent secretory-absorptive capacity that enables the epithelium to contribute significantly to the physiologic formation of bile. The focus of the Physiology Section of the laboratory is to understand the role of cytoskeletal linking proteins in sequestering specific transport and regulatory proteins within membrane microdomains and moderating the transepithelial fluxes of ions, solutes and water across the epithelium. As an example, our laboratory discovered an epithelial cell-specific form of Shank2E. This protein links a number of specific transport proteins to the actin cytoskeleton underlying the apical, microvillar membrane. More recent studies suggest that Shank2E is a central protein in the regulated recovery of these proteins from the microvillar membrane.
‘Apical TIRF’ refines live cell imaging of the apical domain of OK cells.
(left image) By expressing fluorescence-tagged proteins in live OK epithelial cells, TIRF shows co-localization of NaPiIIa (green) and Shank2E (red) within microvilli. Shank2E is a cytoskeletal linking protein that tethers NaPiIIa at the microvillar membrane and likely contributes to the regulated endocytic recovery of NaPiIIa from the microvillar membrane. Bars = 5 um.
(right images) At higher magnification, time lapse images demonstrate the individual Shank2E proteins or Shank2E clusters move along the length of microvilli. Frames were taken at 10 sec intervals
The bile duct is site of genesis for a number of liver diseases, including cystic diseases of the liver. The Pathophysiology Section of our laboratory currently investigates the mechanisms that underlie the growth of liver cysts. These findings will direct the development of medical therapies to intercede in growth and pathology associated with liver cysts. An area of interest is the role of cytokines and growth factors play in driving liver cyst growth. For example, our recent studies have demonstrated that in vivo inhibition of VEGF signaling markedly diminishes the growth of liver cysts during the lifetime of the animal.
Inhibition of VEGF signaling blocks liver cyst growth.
In pkd2(WS25/-) mice, long-term in vivo treatment with SU5416, an inhibitor of VEGF receptor-1 and receptor-2 profoundly blocked the growth of liver cysts. (upper image) At 12 months of age, liver cysts in vehicle-treated animals undergo substantial growth away from the body of the liver. (lower image) At 12 months of age, livers from SU5416-treated animals still have observable liver cysts but the size of the cysts are markedly smaller.
Comparison of liver:body weight ratios confirmed these qualitative observations (data not shown). Livers from SU5416 treated livers from pkd2(WS25/-) mice are not significantly different than livers from pkd2(+/+) mice. Livers from vehicle-treated pkd2(WS25/-) mice are twice as large as livers from pkd2(+/+) mice.