In the heart and its constituent muscle cells stretch is a major determinant of both the strength of cardiac contraction and the rate of secretion of protein hormones. We have shown that caveolae, abundant small vesicular invaginations of the plasma membrane, change their shape during stretch and what may be an analogous process, hyperosmotic shrinkage. These organelles may thus be part of the apparatus that transduces stretch signals in cardiomyocytes. During the previous grant period we have made significant progress on identification and purification of cardiac caveolae and their constituent proteins. Recently, we have made a breakthrough in this area by using an immunopurification protocol with antibodies directed against the muscle- specific caveolin-3 isoform. This improvement now allows us to ask a series of specific questions about the structure and function of cardiac caveolae and their relationship to perturbations such as stretch and osmolarity. There are three specific aims:
Specific Aim 1 will (a) use immunoelectron microscopy to track the internalization of aquaporin1 from caveolae to an as yet unidentified locus in the atrial cytoplasm or elsewhere, (b) identify and localize the vesicles and microtubules involved, (c) look for and study the associated phosphorylations and signaling mechanism, and (d) determine if steps (a - c) manifest stretch dependence.
Specific Aim 2 will (a) use a newly made rabbit polyclonal antibody to the muscle specific caveolin isoform, cav3 to optimize caveolar isolation from sheep and rat hearts; (b) use immuno-electron microscopy to identify immuno-purified caveolae, and standard analytic methods to identify specific lipid and protein components; (c) use microscale (e.g., electrospray) methods to define the protein composition of caveolae (d) study the signaling events in immunopurifed caveolae, and look for reversible phosphorylation, ADP-ribosylation, and effects of stretch.
Specific Aim 3 examines the interaction of caveolae with the recently discovered extracellular matrix protein T-cadherin and the medically interesting caveolae-associated cytoskeletal protein dystrophin and its membrane anchor dystroglycan.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL054302-06
Application #
6184351
Study Section
Cardiovascular and Renal Study Section (CVB)
Project Start
1995-04-01
Project End
2002-06-30
Budget Start
2000-07-01
Budget End
2001-06-30
Support Year
6
Fiscal Year
2000
Total Cost
$360,115
Indirect Cost
Name
University of Chicago
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
005421136
City
Chicago
State
IL
Country
United States
Zip Code
60637
Doyle, Donald D; Upshaw-Earley, Judy; Bell, Eric et al. (2003) Expression of caveolin-3 in rat aortic vascular smooth muscle cells is determined by developmental state. Biochem Biophys Res Commun 304:22-5
Doyle, Donald D; Upshaw-Earley, Judy; Bell, Eric L et al. (2002) Natriuretic peptide receptor-B in adult rat ventricle is predominantly confined to the nonmyocyte population. Am J Physiol Heart Circ Physiol 282:H2117-23
Doyle, D D; Goings, G; Upshaw-Earley, J et al. (2000) Dystrophin associates with caveolae of rat cardiac myocytes: relationship to dystroglycan. Circ Res 87:480-8
Doyle, D D; Goings, G E; Upshaw-Earley, J et al. (1998) T-cadherin is a major glycophosphoinositol-anchored protein associated with noncaveolar detergent-insoluble domains of the cardiac sarcolemma. J Biol Chem 273:6937-43
Page, E; Winterfield, J; Goings, G et al. (1998) Water channel proteins in rat cardiac myocyte caveolae: osmolarity-dependent reversible internalization. Am J Physiol 274:H1988-2000
Doyle, D D; Ambler, S K; Upshaw-Earley, J et al. (1997) Type B atrial natriuretic peptide receptor in cardiac myocyte caveolae. Circ Res 81:86-91