Abstract
Proper growth and development require the orderly synthesis and deposition of individual components of the extracellular matrix (ECM) into well ordered networks. Once formed, the ECM maintains tissue structure and houses resident cells. One ECM component, (beta)ig-h3, is a highly conserved transforming growth factor-beta-inducible protein that has been hypothesized to function as a bifunctional linker between individual matrix components and resident cells. To gain insights into its physiological function, full-length (beta)ig-h3 protein was produced using a baculovirus expression system and purified under native conditions. Human fibroblasts attached and spread on (beta)ig-h3-coated plates and developed actin stress fibers. Purified (beta)ig-h3 binds fibronectin (FN) and type I collagen (Col I) but does not bind gelatin. Using defined fragments of FN, we localized the (beta)ig-h3 recognition region to the gelatin/collagen binding domain present in the N-terminal region of the FN molecule. Our results identify FN and Col I as two ligands of (beta)ig-h3 in the ECM.
Highlights
The ECM1 is composed of an extensive array of macromolecules, which interact to form a highly organized structural network
The structural integrity of the extracellular matrix (ECM) is necessary for proper organ development and function
Matrix structure is in turn determined by precise interactions among individual matrix components [1,2,3,4,5]. ig-h3 is a recently described matrix protein present in the ECM of bladder, lung, and other organ systems
Summary
The ECM1 is composed of an extensive array of macromolecules, which interact to form a highly organized structural network (reviewed in Ref. 1) This matrix is synthesized in a highly regulated fashion [2], and once assembled, it serves as a framework to maintain tissue architecture and house resident cells. In bovine tissues, ig-h3 was found with collagen fibers in developing nuchal ligament, aorta, lung, and mature cornea [11]. It was present in capsule and tubule basement membranes of developing kidney and reticular fibers in fetal spleen. In addition to being a structural component of the ECM, ig-h3 and its relatives may regulate bone production by osteoblasts
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