Abstract
EMILIN-3 is a glycoprotein of the extracellular matrix belonging to a family that contains a characteristic N-terminal cysteine-rich EMI domain. Currently, EMILIN-3 is the least characterized member of the elastin microfibril interface-located protein (EMILIN)/Multimerin family. Using RNA, immunohistochemical, and protein chemistry approaches, we carried out a detailed characterization of the expression and biochemical properties of EMILIN-3 in mouse. During embryonic and postnatal development, EMILIN-3 showed a peculiar and dynamic pattern of gene expression and protein distribution. EMILIN-3 mRNA was first detected at E8.5-E9.5 in the tail bud and in the primitive gut, and at later stages it became abundant in the developing gonads and osteogenic mesenchyme. Interestingly and in contrast to other EMILIN/Multimerin genes, EMILIN-3 was not found in the cardiovascular system. Despite the absence of the globular C1q domain, immunoprecipitation and Western blot analyses demonstrated that EMILIN-3 forms disulfide-bonded homotrimers and higher order oligomers. Circular dichroism spectroscopy indicated that the most C-terminal part of EMILIN-3 has a substantial α-helical content and forms coiled coil structures involved in EMILIN-3 homo-oligomerization. Transfection experiments with recombinant constructs showed that the EMI domain contributes to the higher order self-assembly but was dispensable for homotrimer formation. EMILIN-3 was found to bind heparin with high affinity, a property mediated by the EMI domain, thus revealing a new function for this domain that may contribute to the interaction of EMILIN-3 with other extracellular matrix and/or cell surface molecules. Finally, in vitro experiments showed that EMILIN-3 is able to function as an extracellular regulator of the activity of TGF-β ligands.
Highlights
elastin microfibril interface-located protein (EMILIN)-3 is the least characterized member of the EMILIN/Multimerin family
Despite a high degree of conservation of global protein organization with the other EMILINs/Multimerins, EMILIN-3 is lacking the C-terminal globular C1q (gC1q) domain that is present in all other members of the family [2]
Our in situ hybridization data show that during mouse development EMILIN-3 has a dynamic pattern of expression, which only partially overlaps with the expression patterns of other EMILIN/Multimerin genes [2, 14]
Summary
EMILIN-3 is the least characterized member of the EMILIN/Multimerin family. Results: EMILIN-3 forms homotrimers and higher order oligomers, binds heparin, has a dynamic expression during development and a restricted distribution in adult tissues, and serves as a pro-TGF- antagonist. During embryonic and postnatal development, EMILIN-3 showed a peculiar and dynamic pattern of gene expression and protein distribution. EMILINs/Multimerins contain various regions endowed with oligomerization capability, such as the gC1q and EMI domains, collagen repeats, and long regions potentially forming coiled coil structures. The effective formation of coiled coil structures in these proteins was never demonstrated until now, it was suggested that coiled coil stretches and the gC1q domain may be implicated in the oligomerization of EMILINs/Multimerins into higher order structures. Previous studies have provided information on the expression pattern of some EMILIN/Multimerin genes during mouse development [2, 7, 14]. We present a detailed study of the expression of EMILIN-3 during mouse embryonic and postnatal development together with a characterization of the biochemical properties of the endogenous protein and its recombinant products
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
