EMILIN1

EMILIN1 Full Name

elastin microfibril interfacer 1

EMILIN1 Introduction

EMILIN1 encodes elastin microfibril interfacer 1, an extracellular matrix glycoprotein that helps build and organize the elastic fibers that give tissues such as blood vessels, lungs, and skin their resilience. The protein was discovered as a component that localizes to the interface between elastin and the microfibrils that surround it, a position that suggested a role in connecting the two parts of the elastic fiber, and its name records this location. EMILIN1 is a large, multidomain protein that can self-assemble into homotrimers, and it is expressed by smooth muscle cells, endothelial cells, fibroblasts, and other matrix-producing cells in tissues rich in elastic fibers. Beyond its structural functions, EMILIN1 has emerged as a signaling molecule that regulates the bioavailability of transforming growth factor-beta (TGF-beta), a cytokine that controls cell proliferation, differentiation, and matrix production: EMILIN1 binds the latent form of TGF-beta and thereby limits its activation, providing a molecular link between the extracellular matrix and cell signaling. Consistent with these functions, mice lacking EMILIN1 show defects in elastogenesis and in the structure of the vasculature and other elastic tissues. EMILIN1 has also been connected to human disease through mutations that impair its secretion, causing a form of hereditary lymphedema, and through its altered expression in cancer, where changes in the matrix can influence tumor invasion and the response of cells to growth factors.

Figure 1. The structure of EMILIN1.

Multidomain Matrix Glycoprotein and Trimeric Assembly
EMILIN1 is a modular glycoprotein whose N-terminal EMI domain, a cysteine-rich module, is responsible for the trimerization of the protein into its characteristic bouquet-like structure.
Following the EMI domain are EGF-like repeats, a central collagenous segment, and a C-terminal gC1q domain that is homologous to the globular domain of complement component C1q.
The EMILIN1 gene is located on human chromosome 2, and the protein is synthesized as a precursor that is proteolytically processed during secretion and deposition into the matrix.
Within the extracellular matrix, EMILIN1 associates with elastic fibers and with microfibrils, and its location at the elastin-microfibril interface suggested its name and its proposed function as an interfacer between these structures.
The gC1q domain mediates interactions with cells: it binds integrins, including alpha4beta1, allowing EMILIN1 to support cell adhesion and to influence cell migration.
EMILIN1 also interacts with components of the elastic fiber system, such as fibulin and fibrillin, contributing to the supramolecular organization of the matrix.
The ability of EMILIN1 to self-assemble into trimers, combined with its multiple binding partners, allows it to bridge matrix components and cells within elastic tissues.

Elastic Fiber Assembly, TGF-Beta Regulation, and Disease Connections
In elastic tissues, EMILIN1 contributes to the assembly and organization of elastic fibers, and its absence in knockout mice leads to abnormalities of the aorta and other vessels, including altered elastin architecture and vessel wall mechanics.
EMILIN1 regulates the bioavailability of TGF-beta by binding the large latent complex that contains the cytokine, and its interaction with the latent TGF-beta binding protein limits the release of active TGF-beta.
Because TGF-beta controls the expression of matrix proteins and the behavior of smooth muscle cells, the regulation of TGF-beta by EMILIN1 feeds back on the composition and function of the vessel wall.
Mutations in EMILIN1 have been identified in families with hereditary lymphedema, and functional studies show that these mutations impair the secretion or matrix deposition of the protein, linking EMILIN1 to the development of the lymphatic system.
In cancer, the expression of EMILIN1 is frequently reduced in tumor tissue, and loss of the protein has been associated with enhanced tumor invasion and metastasis, consistent with a role for the matrix in restraining malignant cells.
Because EMILIN1 sits at the interface of matrix structure and growth factor signaling, it represents a potential target for modulating fibrosis, vascular disease, and tumor progression through manipulation of the extracellular microenvironment.

Alternate Names for EMILIN1

EMILIN1; elastin microfibril interfacer 1; EMILIN-1; DKFZp586M121; gp115; elastin microfibril interface located protein; elastin microfibril interface-located protein 1; EMI; EMILIN;