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Blood, 1 April 2006, Vol. 107, No. 7, pp. 2713-2719. Prepublished online as a Blood First Edition Paper on November 22, 2005; DOI 10.1182/blood-2005-07-2990. This Article Full Text (PDF) All Versions of this Article: 2005-07-2990v1 107/7/2713    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Rights and Permissions Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Mitchell, W B Articles by Coller, B. S Search for Related Content PubMed PubMed Citation Articles by Mitchell, W B Articles by Coller, B. S Social Bookmarking                   What's this?  Previous Article  |  Next Article  Submitted July 26, 2005 Accepted November 13, 2005 IIb3 biogenesis is controlled by engagement of IIb in the calnexin cycle via the N15-linked glycan W B Mitchell*, JiHong Li, Deborah L French, and Barry S Coller Department of Pediatrics, Mount Sinai School of Medicine, New York, NY, USA; Laboratory for Blood and Vascular Biology, The Rockefeller University, New York, NY, USA Laboratory for Blood and Vascular Biology, The Rockefeller University, New York, NY, USA Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY, USA * Corresponding author; email: mitcheb{at}rockefeller.edu. Although much is known about IIb3 structure and function, relatively little is understood about its biogenesis. Thus, we studied the kinetics of pro-IIb production and degradation, focusing on whether proteasomal degradation and/or the calnexin cycle participate in these processes. In pulse-chase analyses, the time to half-disappearance of pro-IIb (t1/2) was the same in: 1) HEK293 cells transfected with a) IIb+3, b) IIb alone, c) mutant V298FIIb+3 or d) I374TIIb+3; and 2) murine wildtype and 3-null megakaryocytes. Inhibition of the proteasome prolonged the t1/2 values in both HEK293 cells and murine megakaryocytes. Calnexin coprecipitated with IIb from HEK293 cells transfected with IIb alone, V298FIIb+3, and I374TIIb+3, but not from cells cotransfected with normal IIb+3. For proteins in the calnexin cycle, loss of the terminal mannose residue of the middle branch of the core N-linked glycan results in degradation. Inhibition of the enzyme that removes this mannose residue prevented pro-IIb degradation in 3-null murine megakaryocytes. IIb contains a conserved glycosylation consensus sequence at N15, and an N15Q mutation prevented pro-IIb maturation, complex formation, and degradation. Our findings suggest that pro-IIb engages the calnexin cycle via the N15 glycan, and that failure of pro-IIb to complex normally with 3 results in proteasomal degradation. CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this? This article has been cited by other articles: W. Beau Mitchell, J. Li, M. Murcia, N. Valentin, P. J. Newman, and B. S. Coller Mapping early conformational changes in {alpha}IIb and {beta}3 during biogenesis reveals a potential mechanism for {alpha}IIb{beta}3 adopting its bent conformation Blood, May 1, 2007; 109(9): 3725 - 3732. [Abstract] [Full Text] [PDF]

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