Endocytosis and storage of plasma factor V by human megakaryocytes.
Thromb Haemost
; 94(3): 585-92, 2005 Sep.
Article
in En
| MEDLINE
| ID: mdl-16268476
ABSTRACT
Factor V is an essential coagulation cofactor that circulates in plasma and platelet alpha-granules where it is stored complexed to multimerin I (MMRN1). To gain insights into the origin and processing of human platelet factor V, and factor V-MMRN I complexes, we studied factorV in cultured megakaryocytes. Factor V mRNA was detected in all megakaryocyte cultures. However, like albumin, IgG and fibrinogen, factorV protein was detectable only in megakaryocytes cultured with exogenous protein. The amount of factor V associated with megakaryocytes was influenced by the exogenous factorV concentration. Similar to platelet factor V, megakaryocyte factor V was proteolyzed and complexed with megakaryocyte-synthesized MMRN1. With secretagogues, megakaryocytes released factor V, IgG, fibrinogen and MMRN1. Immunofluorescent and electron microscopy confirmed factorV uptake by endocytosis and its trafficking to megakaryocyte alpha-granules. These data provide direct evidence that human megakaryocytes process plasma-derived factor V into alpha-granules and generate factorV-MMRN I complexes from endogenously and exogenously synthesized proteins.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Factor V
/
RNA, Messenger
/
Megakaryocytes
/
Endocytosis
Limits:
Humans
Language:
En
Journal:
Thromb Haemost
Year:
2005
Document type:
Article
Affiliation country:
Canada