Tissue factor encryption/de-encryption is not altered in the absence of the cytoplasmic domain.
Since the cytoplasmic domain of tissue factor (TF) appears to have a role in TF function beyond coagulation, experiments were conducted to determine whether the cytoplasmic domain also has a role in regulating procoagulant activity of TF present in the cell membrane. TF encryption was quantitated in human YU-SITI, U87-MG, and mouse 3T3 cells which were transfected for expression of human tissue factor or a construct lacking the cytoplasmic domain (TF(CD)). Comparison of intact cells (encrypted) with fully disrupted cells (de-encrypted) showed that TF and TF(CD) were equally encrypted with respect to function in fX activation. Moreover, cells expressing TF and TF(CD) were indistinguishable in their procoagulant responses to A23187-calcium and varied concentrations of nonionic detergents. TF in membrane vesicles spontaneously shed by U87-MG cells was largely, but incompletely, de-encrypted, and the degree of de-encryption was independent of the cytoplasmic domain. We conclude that the predominant mechanism(s) for encrypting TF procoagulant activity is independent of the cytoplasmic domain.
Carson
S D
SD
Department of Pathology and Microbiology, University of Nebraska Medical Center, Nebraska Medical Center, Omaha 68198-6495, USA. 73632.3623@compuserve.com
Bromberg
M E
ME
D000818:Animals; D002460:Cell Line; D006801:Humans; D051379:Mice; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D013925:Thromboplastin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D011994:Recombinant Proteins; D013925:Thromboplastin