Linked Life Data

2167306

Source:http://linkedlifedata.com/resource/pubmed/id/2167306

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
24
pubmed:dateCreated
1990-9-27
pubmed:abstractText
Complexes between tissue-type plasminogen activator (t-PA) and its rapidly acting inhibitor plasminogen activator inhibitor type 1 (PAI-1) are bound, internalized, and degraded by HepG2 cells. The mechanism involves endocytosis mediated by a specific high-affinity receptor. However, the particular domains of the complex that are recognized by the receptor have not been elucidated. To identify the determinants involved in ligand binding to the receptor, several variants of t-PA were assessed for their ability to form complexes with PAI-1 and thereby to inhibit specific cellular binding of complexes between structurally unmodified 125I-t-PA and PAI-1. Catalytically active variants lacking selected structural domains form complexes with PAI-1 and inhibit 125I-t-PA.PAI-1 binding to HepG2 cells. In addition, several forms of the plasminogen activator urokinase (u-PA), which shares partial structural homology with t-PA, were evaluated as competitors of cellular binding. The catalytically active two-chain forms of u-PA, but not the inactive proenzyme single-chain form, complex with PAI-1 and inhibit specific binding of 125I-t-PA.PAI-1, suggesting that the serine protease domain, rather than other domains, may confer the determinants required for cellular binding. However, a mutant t-PA with markedly reduced catalytic activity, resulting from replacement of the active site serine with threonine, not only forms complexes with PAI-1 but also inhibits specific cellular binding of unmodified 125I-t-PA.PAI-1. These data indicate that specific binding of t-PA.PAI-1 to HepG2 cells does not require a serine-containing catalytic site in the protease domain. To determine whether binding of the complex is mediated through other components of t-PA or through structural elements of PAI-1, both t-PA and PAI-1 were examined separately for capacity to bind directly to HepG2 cells. To exclude potential interactions with components of the extracellular matrix which contains binding sites for PAI-1, ligand binding to HepG2 cells in suspension was assessed. Although neither t-PA nor PAI-1 alone binds specifically to HepG2 cells, the preformed t-PA.PAI-1 complexes do. These findings suggest that specific binding of t-PA.PAI-1 requires elements of the PAI-1 moiety and/or parts of the protease domain of t-PA.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
25
pubmed:volume
265
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
14093-9
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
1990
pubmed:articleTitle
Identification of determinants involved in binding of tissue-type plasminogen activator-plasminogen activator inhibitor type 1 complexes to HepG2 cells.
pubmed:affiliation
Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't