LEUCINE-RICH REPEAT GLYCOPROTEINS OF THE EXTRACELLULAR-MATRIX

The extracellular matrix plays an integral role in the pivotal process es of development, tissue repair, and metastasis by regulating cell pr oliferation, differentiation, adhesion, and migration. This review is focused on a family of related? glycoproteins represented by at least one member in all specialized extracellular matrices. This family curr ently comprises nine members grouped together on the basis of their pr esence in the extracellular matrix and by virtue of a leucine-rich rep eat motif tl-lat dominates the structure of the core protein. It is li kely that most, if not all the members of this group exist as proteogl ycans in some tissues, and thus have been termed the Small Leucine-Ric h Proteoglycan family, or SLRPs. The leucine-rich repeat (LRR) is usua lly present in tandem array and has been described in an increasing nu mber of proteins, giving rise to a LRR-superfamily. The LRR domain of the SLRP family is unique within the superfamily in that it is flanked by cysteine clusters, and the 24 amino acid con sensus for SLRP membe rs is x-x-x-F/P/L-x-x-L/P-x-x-L-x-x-L/I-x-L-x-x-N-x-I/L, where x is an y amino acid. Enormous progress has been made in describing the member ship, structure and localization of this family, and recently new insi ght has emerged into the putative function of these molecules not just as modulators of matrix assembly but also on their intriguing role in regulating cell growth, adhesion, and migration. Determination of mem bership, structure and putative function of this fascinating class of molecules is summarized in this review.