T-cadherin is a major glycophosphoinositol-anchored protein associated with noncaveolar detergent-insoluble domains of the cardiac sarcolemma.
Sucrose-density flotation analysis of Triton-insoluble membrane domains isolated from highly purified sheep ventricular sarcolemma revealed the presence of two major 120- and 100-kDa proteins. Both species migrated in two-dimensional isoelectric focussing/SDS gels with an apparent pI of approximately 4.3, suggesting that they might be related. Microsequence analysis of peptides derived from the 100-kDa protein yielded amino acid sequences with high homology to T-cadherin, a truncated cadherin lacking a cytoplasmic domain. The similarity was confirmed using antibodies to chicken T-cadherin that reacted with both proteins on immunoblots. T-cadherin was released from the detergent-insoluble sarcolemmal fraction by phospholipase C treatment indicating that it is linked to the membrane by a glycophosphoinositol anchor. T-cadherin could be ADP-ribosylated by a transferase that was also present in the caveolin-enriched Triton-insoluble fraction. T-cadherin-containing membrane fragments cofractionated on sucrose gradients with caveolin-3, a marker protein for myocyte caveolae. However, immunopurified caveolin-3-containing membranes contained no associated T-cadherin. Immunocytochemical analysis of cultured rat atrial myocytes revealed that T-cadherin and caveolin have related but nonoverlapping staining patterns. These results suggest that T-cadherin is a major glycophosphoinositol-linked protein in cardiac myocytes and that it may be located in plasma membrane "rafts" distinct from but possibly adjacent to caveolae.
Doyle
D D
DD
Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA.
Goings
G E
GE
Upshaw-Earley
J
J
Page
E
E
Ranscht
B
B
Palfrey
H C
HC
D000595:Amino Acid Sequence; D000818:Animals; D015820:Cadherins / Q000737:chemistry / Q000378:metabolism*; D051244:Caveolin 3; D022461:Caveolins; D003902:Detergents; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000737:chemistry / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D017830:Octoxynol; D012508:Sarcolemma / Q000378:metabolism* / Q000648:ultrastructure; D012756:Sheep; D012995:Solubility
D015820:Cadherins; D051244:Caveolin 3; D022461:Caveolins; D003902:Detergents; D017261:Glycosylphosphatidylinositols; C099972:H-cadherin; D008565:Membrane Proteins; D009124:Muscle Proteins; D017830:Octoxynol