Calreticulin-integrin bidirectional signaling complex.
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| Abstract |
Calreticulin has multiple functions, diverse cellular locations, and putative isoforms. It likely maintains integrin avidity by binding alpha integrin cytoplasmic tails and is a surface lectin which triggers cell spreading. In the present study, we have immunocaptured a cell surface complex from B16 mouse melanoma cells which contains alpha 6 beta 1 integrin, two molecular forms of calreticulin, and KDEL docking protein (KDEL-R). One of the calreticulins, "endocalreticulin", a 52 kDa protein, does not become surface biotinylated, and is probably bound to alpha integrin cytoplasmic tails; it disappears when B16 cells adhere to laminin, and two ubiquitinated calreticulins appear. One ubiquitinated species, a 125 kDa protein, is restricted to focal contacts whereas a second species, a 75 kDa protein, is in focal contacts and surrounding plasma membrane; it also arises when cells bind non-specific surfaces. The other calreticulin, "ectocalreticulin", a 62 kDa protein, becomes surface biotinylated, is probably anchored to surface KDEL-R, and cooperates with alpha 6 beta 1 integrin, triggering cell spreading. The present results suggest a model in which calreticulin-integrin surface complex functions as a symbiotic unit, transmitting information in both directions across the plasma membrane.
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| Authors | Q Zhu, P Zelinka, T White, M L Tanzer |
| Journal | Biochemical and biophysical research communications (Biochem Biophys Res Commun) Vol. 232 Issue 2 Pg. 354-8 (Mar 17 1997) ISSN: 0006-291X [Print] United States |
| PMID | 9125180 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.) |
| Chemical References |
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