EMILIN, a Component of the Elastic Fiber and a New Member of the C1q/Tumor Necrosis Factor Superfamily of Proteins

Abstract

EMILIN (elastin microfibril interface located protein)is an extracellular matrix glycoprotein abundantly expressed in elastin-rich tissues such as blood vessels, skin, heart, and lung. It occurs associated with elastic fibers at the interface between amorphous elastin and microfibrils. Avian EMILIN was extracted from 19-dayold embryonic chick aortas and associated blood vessels and purified by ion-exchange chromatography and gel filtration. Tryptic peptides were generated from EMI-LIN and sequenced, and degenerate inosine-containing oligonucleotide primers were designed from some peptides. A set of primers allowed the amplification of a 360-base pair reverse transcription polymerase chain reaction product from chick aorta mRNA. A probe based on a human homologue selected by comparison of the chick sequence with EST data base was used to select overlapping clones from both human aorta and kidney cDNA libraries. Here we present the cDNA sequence of the entire coding region of human EMILIN encompassing an open reading frame of 1016 amino acid residues. There was a high degree of homology (76% identity and 88% similarity) between the chick C terminus and the human sequence as well as between the N terminus of the mature chick protein where 10 of 12 residues, as determined by N-terminal sequencing, were identical or similar to the deduced N terminus of human EMILIN. The domain organization of human EMILIN includes a C1q-like globular domain at the C terminus, a collagenous stalk, and a longer segment in which at least four heptad repeats and a leucine zipper can be identified with a high potential for forming coiled-coil ␣ helices. At the N terminus there is a cysteine-rich sequence stretch similar to a region of multimerin, a platelet and endothelial cell component, containing a partial epidermal growth factor-like motif. The native state of the recombinantly expressed EMILIN C1q-like domain to be used in cell adhesion was determined by CD spectra analysis, which indicated a high value of ␤-sheet conformation. The EMILIN C1q-like domain promoted a high cell adhesion of the leiomyosarcoma cell line SK-UT-1, whereas the fibrosarcoma cell line HT1080 was negative.

Molecular Cloning and Characterization of EndoGlyx-1, an EMILIN-like Multisubunit Glycoprotein of Vascular Endothelium

“…There are two well conserved regions in the C1q domain: an aromatic motif (amino acids 844 -873) as defined by the Prosite C1q pattern is located within the first part of the domain (amino acids 827-873), the other conserved region is near the extreme C terminus (amino acids 912-947). A C-terminal C1q domain is a common feature of the C1q-family of proteins such as the A, B, and C chains of the complement C1q protein (15,16), the type VIII and X collagens (17,18), the recently identified and broadly expressed extracellular matrix glycoprotein EMILIN (19), and a large protein of homomultimeric structure called multimerin (20) found in the ␣-granules of platelets and Waibel-Palade bodies of endothelium.…”

Ultrastructural properties of ciliary zonule microfibrils

“…In addition to the fibrillins, many other proteins have been reported to be either microfibril constituents or microfibril-associated proteins. These include the two microfibril-associated glycoproteins, MAGP-1 and MAGP-2 (Gibson et al, 1986(Gibson et al, , 1991, associated microfibril protein (AMP; Horrigan et al, 1992), EMI-LIN, a 115-kDa protein that appears to be preferentially localize to the elastin-microfibril interface (Bressan et al, 1993;Doliana et al, 1999), a 36-kDa protein isolated from porcine aorta (Kobayashi et al, 1989), fibulin-2 (Reinhardt et al, 1996) and fibulin-5 (Yanagisawa et al, 2002), latent TGF-b-binding protein-2 (LTBP-2) , endostatin (Miosge et al, 1999), and proteoglycans (Kielty et al, 1996;Trask et al, 2000).…”

An Alternative Role of C1q in Cell Migration and Tissue Remodeling: Contribution to Trophoblast Invasion and Placental Development

“…Elastin microfibril interfacer 1 (EMILIN1) is a connective tissue glycoprotein associated with elastic fibers (22) previously identified as another candidate ECM molecule involved in EVT invasion. A characteristic feature of this protein is to display a gradient distribution in decidua with a progressive increase in its expression toward remodeled spiral arteries that favors EVT migration from the anchoring columns to the perivascular areas (23).…”