Analyses of cellular multimerin 1 receptors: in vitro evidence of binding mediated by αΙΙbβ3 and αvβ3

Abstract

Multimerin 1 (MMRN1) is a large, soluble, polymeric, factor V binding protein and member of the EMILIN protein family. In vivo, MMRN1 is found in platelets, megakaryocytes, endothelium and extracellular matrix fibers, but not in plasma. To address the mechanism of MMRN1 binding to activated platelets and endothelial cells, we investigated the identity of the major MMRN1 receptors on these cells using wild-type and RGE-forms of recombinant MMRN1. Ligand capture, cell adhesion, ELISA and flow cytometry analyses of platelet-MMRN1 binding, indicated that MMRN1 binds to integrins alphaIIbbeta3 and alphavbeta3. Endothelial cell binding to MMRN1 was predominantly mediated by alphavbeta3 and did not require the MMRN1 RGD site or cellular activation. Like many other alphavbeta3 ligands, MMRN1 had the ability to support adhesion of additional cell types, including stimulated neutrophils. Expression studies, using a cell line capable of endothelial-like MMRN1 processing, indicated that MMRN1 adhesion to cellular receptors enhanced its extracellular matrix fiber assembly. These studies implicate integrin-mediated binding in MMRN1 attachment to cells and indicate that MMRN1 is a ligand for alphaIIbbeta3 and alphavbeta3.

RNA Profiling Analysis of the Serum Exosomes Derived from Patients with Active and Latent Mycobacterium tuberculosis Infection

“…As for the ATB highly expressed groups (Supplementary Figure 2), 12 genes displayed an increased trend and were in agreement with the previous studies (Pacis et al, 2015) (Supplementary Table 4). Among which, ACSL4 and CLU were related with lipid metabolic process (Kuch et al, 2014; Park et al, 2014), and MMRN1 and POSTN were relevant to cell adhesion (Adam et al, 2005; Michaylira et al, 2010). These results suggested that the top-20 genes for each pattern might provide potential molecular targets for the prevention, diagnosis, and treatment of LTBI and ATB individuals.…”

Multimerin-1 (MMRN1) as Novel Adverse Marker in Pediatric Acute Myeloid Leukemia: A Report from the Children's Oncology Group

“…Forming a variety of di-sulfide linked multimers, ranging from a trimeric complex to multimers of many megadaltons in size (14), it is conceivable that MMRN1 could play a dynamic role in the cytoarchitectural and adhesive changes that accompany platelet aggregation and clot formation. Together, MMRN1 may therefore serve as an extracellular matrix (ECM) or adhesive protein mediating cellular attachment through the binding of ECM proteins and integrin receptors (15, 16). …”

The EMILIN/Multimerin Family

“…The family includes EMILIN1 (Colombatti et al, 1985; Bressan et al, 1993; Doliana et al, 1999), EMILIN2 (Doliana et al, 2001), Multimerin1 (MMRN1; Hayward et al, 1991, 1995), and Multimerin2 (MMRN2; Sanz-Moncasi et al, 1994; Christian et al, 2001). Apart from MMRN1 that is deposited in the ECM but for the most part is sequestered in megakaryocytes, endothelial cells (ECs), and platelets granules (Adam et al, 2005), the members of the EMILIN family are constituents of the ECM Under normal conditions the expression of each individual gene overlaps with those of some other members of the family; the only exception is apparently the central nervous system, where only EMILIN2 is detected outside blood vessels, at least at the mRNA level (Braghetta et al, 2004). Moreover, EMILIN2 is specifically and abundantly expressed in mouse cochlear basilar membrane (Amma et al, 2003).…”

“…MMRN1 is a soluble S–S linked homopolymer stored in platelets, megakaryocytes, and ECs and deposited in ECM (Hayward, 1997; Adam et al, 2005). It supports the adhesion of platelets, neutrophils, and ECs via integrin αvβ3 and α IIb β3 (Adam et al, 2005).…”