Interaction of mutants of tissue-type plasminogen activator with liver cells: effect of domain deletions

Abstract

The fibrin-specific thrombolyticum tissue-type plasminogen activator (t-PA) has proven to be a potent drug in several clinical trials, but its clinical application is complicated by the rapid clearance of t-PA from the circulation. The rapid plasma clearance of t-PA results from the uptake of t-PA in the liver. t-PA consists of several domains which may be involved in the interaction with the liver. Three domain-deletion mutants, which were produced by the use of a cassette gene system, were studied in vivo and in vitro for their capacity to bind to the various types of rat liver cells. The three mutants lacked, in comparison to control t-PA, the epidermal growth factor (G) domain, the finger (F) domain or the G domain plus the first kringle (K1). The plasma clearance of the three mutants was slower than that of control t-PA. The slower plasma clearance resulted from a decreased liver uptake: 50 and 80% for t-PA mutants and control t-PA respectively. It was found that the K1 domain was of major importance for the uptake of t-PA by liver endothelial cells in vivo and in vitro. The high-affinity binding of t-PA (and t-PA mutants) to parenchymal liver cells depended largely on the presence of the G domain. Other domain(s), like the F, K2 or protease domain, may be responsible for low-affinity, t-PA-specific binding to rat parenchymal liver cells.

Hepatocyte growth factor and alternative splice variants - expression, regulation and implications in osteogenesis and bone health and repair

“…Similar to the synthesis pathway of HGF, plasminogen is secreted by the liver as an inactive single polypeptide enzyme that is activated by the actions of a serine-protease and is consequently converted into plasmin, a disulfide linked heterodimer 14 . The physiologic function of plasmin is the degradation of fibrin proteins present in blood clots 15 . Additionally, it is hypothesized that HGF, macrophage stimulating protein (MSP), plasminogen, and apolipoprotein retain a shared genetic precursor.…”

Hepatocyte growth factor/scatter factor‐induced intracellular signalling

“…1991). Its organization highly resembles that of factors implicated in blood coagulation and fibrinolysis, such as plasminogen and prothrombin (Kuiper et al . 1996).…”

Serine-proteases as plasminogen activators in terms of fibrinolysis

“…[58] The fundamental problem with alteplase is its short half-life in the blood circulation (4-6 min) so that large doses are needed, given as infusions over 90 min after an initial bolus, and in that way the specificity of cleaving fibrin-bound plasminogen is lost. [59][60] Nevertheless alteplase is the standard fibrinolytic agent.…”

“…Alteplase (rt-PA) Human [2], [29][30][31][32][33][34][35][36][37][38][39][40], [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59] Gly-Pro-Arg (GPR) at the a-chain and Gly-His-Arg (GHR) at the b-chain. They are positively charged and are called 'knobs' , leading to polymerization by non-covalent interaction with negatively charged 'holes' in the carboxy-terminal region of the g-chain (a-g) or b-chain (b-b) of other fibrin monomers.…”