Fibulin-5 binds urokinase-type plasminogen activator and mediates urokinase-stimulated β1-integrin-dependent cell migration

Abstract

uPA (urokinase-type plasminogen activator) stimulates cell migration through multiple pathways, including formation of plasmin and extracellular metalloproteinases, and binding to the uPAR (uPA receptor; also known as CD87), integrins and LRP1 (low-density lipoprotein receptor-related protein 1) which activate intracellular signalling pathways. In the present paper we report that uPA-mediated cell migration requires an interaction with fibulin-5. uPA stimulates migration of wild-type MEFs (mouse embryonic fibroblasts) (Fbln5+/+ MEFs), but has no effect on fibulin-5-deficient (Fbln5−/−) MEFs. Migration of MEFs in response to uPA requires an interaction of fibulin-5 with integrins, as MEFs expressing a mutant fibulin-5 incapable of binding integrins (FblnRGE/RGE MEFs) do not migrate in response to uPA. Moreover, a blocking anti-(human β1-integrin) antibody inhibited the migration of PASMCs (pulmonary arterial smooth muscle cells) in response to uPA. Binding of uPA to fibulin-5 generates plasmin, which excises the integrin-binding N-terminal cbEGF (Ca2+ -binding epidermal growth factor)-like domain, leading to loss of β1-integrin binding. We suggest that uPA promotes cell migration by binding to fibulin-5, initiating its cleavage by plasmin, which leads to its dissociation from β1-integrin and thereby unblocks the capacity of integrin to facilitate cell motility.

Fibulin-3, -4, and -5 Are Highly Susceptible to Proteolysis, Interact with Cells and Heparin, and Form Multimers

“…For fibulin-5, a two-band pattern of recombinant human fibulin-5 has been described previously by two groups 19,39). Hirai et al (19) observed that fibulin-5 was preferentially cleaved in aged mice and identified a cleavage site at position Arg 77 of recombinant human fibulin-5 that is also located within the N-terminal linker region.…”

Fibulin-4 and fibulin-5 in elastogenesis and beyond: Insights from mouse and human studies

“…Interestingly, fibulin-5 was shown to be hypermethylated and the expression was downregulated in primary tumors and lung cancer cell lines, contributing to an increase in cancer cell invasion (Yue et al, 2009). More recently, fibulin-5 was shown to be required for urokinase-type plasminogen activator (uPA)-mediated cell migration (Kapustin et al, 2012). Interaction between uPA and fibulin-5 resulted in generation of plasmin, which cleaves the N-terminal cbEGF-like domain of fibulin-5 containing the integrin-binding motif and disrupts fibulin-5-β1 integrin binding, releasing the inhibitory effects of fibulin-5 on β1 integrin-mediated cell migration (Kapustin et al, 2012).…”

“…More recently, fibulin-5 was shown to be required for urokinase-type plasminogen activator (uPA)-mediated cell migration (Kapustin et al, 2012). Interaction between uPA and fibulin-5 resulted in generation of plasmin, which cleaves the N-terminal cbEGF-like domain of fibulin-5 containing the integrin-binding motif and disrupts fibulin-5-β1 integrin binding, releasing the inhibitory effects of fibulin-5 on β1 integrin-mediated cell migration (Kapustin et al, 2012). Taken together, these studies point to the role of fibulin-5 in regulating protease activity by interacting with β1 integrin as an endogenous competitive ligand.…”

Role of multidomain structure of urokinase in regulation of growth and remodeling of vessels

“…поскольку было показано, что lrP опос-редует активацию миграции и пролиферации клеток, а также вовлечен в регуляцию прони-цаемости сосудистой стенки [57], мы предпо-ложили, что новая мишень, совместно с lrP, может обеспечивать связывание урокиназы без «ростового» домена с поверхностью кле-ток, а также принимать участие в регуляции ее энзиматической и хемотактической актив-ности. нами была обнаружена новая мишень связывания урокиназы на поверхности клеток, отличная от uPar/cd87, -фибулин-5 [58]. Удалось установить, что урокиназа способна непосредственно взаимодействовать с фибули-ном-5 через протеолитический домен.…”