This project seeks to explore the function of a newly discovered protein, TIMAP, in the development of renal glomerular capillaries and the vasculature in general. We have reported evidence in vitro and in vivo, that TGF-Beta1 signals are necessary for renal glomerular capillary morphogenesis. We now extend our observations to the characterization of a novel TGF-Beta1 responsive gene, and its predicted protein product, which we named TIMAP (TGF-Beta1 inhibited membrane associated protein). In vitro, TIMAP is expressed in endothelial and hematopoietic cells (endothelial and hematopoietic cells are derived from a common lineage), and in vivo TIMAP is expressed predominantly in the vasculature and in renal glomeruli, and TIMAP localizes to endothelial cells and VSMC. We find that TIMAP is the first clearly identified direct intracellular binding partner for the non-integrin 67 kDa laminin receptor (67LR) at the cell membrane. The 67LR is a transmembrane glycoprotein, which interacts specifically and with high affinity with the laminin Beta1 chain. 67LR is a marker for highly motile, metastatic cells in human tumors. In endothelial cells, laminin is required for assembly tubes, and inhibition of the interaction between 67LR and laminin blocks endothelial cell organization into tubes. The 67LR is also required for the upregulation of eNOS in endothelial cells in response to shear stress. To date, the mechanisms whereby signals from the 67LR are transmitted to the cell have not been elucidated. We also find that TIMAP interferes with TGF-Beta1 -stimulated endothelial cell apoptosis, apoptosis being component of TGF-Beta1 stimulated glomerular capillary morphogenesis in vitro. Furthermore, in glomerular capillaries in vivo, TGF-Beta1 is involved in removing superfluous cells through the process of apoptosis, and thereby facilitates capillary lumen formation. The current proposal explores the possibility that TIMAP represents a critical component of a 67LR signaling pathway, and thereby is involved in regulating endothelial cell motility, tube formation, and apoptosis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK050764-10
Application #
6891307
Study Section
Pathology A Study Section (PTHA)
Program Officer
Wilder, Elizabeth L
Project Start
1996-08-01
Project End
2006-04-30
Budget Start
2005-05-01
Budget End
2006-04-30
Support Year
10
Fiscal Year
2005
Total Cost
$202,501
Indirect Cost
Name
University of Alberta
Department
Type
DUNS #
208095844
City
Edmonton
State
AB
Country
Canada
Zip Code
T6 2-E1
Li, Laiji; Kozlowski, Kathy; Wegner, Binytha et al. (2007) Phosphorylation of TIMAP by glycogen synthase kinase-3beta activates its associated protein phosphatase 1. J Biol Chem 282:25960-9
Kim, Kwanghee; Li, Laiji; Kozlowski, Kathy et al. (2005) The protein phosphatase-1 targeting subunit TIMAP regulates LAMR1 phosphorylation. Biochem Biophys Res Commun 338:1327-34
Cao, Wangsen; Mattagajasingh, Subhendra N; Xu, Hangxue et al. (2002) TIMAP, a novel CAAX box protein regulated by TGF-beta1 and expressed in endothelial cells. Am J Physiol Cell Physiol 283:C327-37
Liu, A; Dardik, A; Ballermann, B J (1999) Neutralizing TGF-beta1 antibody infusion in neonatal rat delays in vivo glomerular capillary formation 1. Kidney Int 56:1334-48
Liu, A; Ballermann, B J (1998) TGF-beta type II receptor in rat renal vascular development: localization to juxtaglomerular cells. Kidney Int 53:716-25
Carlson, S G; Eng, E; Kim, E G et al. (1998) Expression of SET, an inhibitor of protein phosphatase 2A, in renal development and Wilms' tumor. J Am Soc Nephrol 9:1873-80
Choi, M E; Liu, A; Ballermann, B J (1997) Differential expression of transforming growth factor-beta receptors in rat kidney development. Am J Physiol 273:F386-95