A NOVEL TYPE II TRANSMEMBRANE MATRIX METALLOPROTEINASE

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DESCRIPTION: (Adapted from the investigator's abstract) The long-term objective of this proposal is to characterize a novel metalloproteinase named CA-MMP (Cysteine-Array Matrix MetalloProteinase)/MMP23 and define its function in remodeling extracellular matrix (ECM). Composed of a diverse group of macromolecules such as collagens and elastins, ECM serves as molecular glue holding cells together to provide the structural scaffold for physical strength as well as developmental cues to specify where and when the cells are in the human body. Aberrant turnover of the ECM has been associated with painful and lethal diseases such as cancer. Malignant tumor cells acquire the invasive and metastatic phenotype in part by regulating the expression of powerful proteolytic enzymes that allow them to destroy the structural barriers made of ECM. Thus, there has been intense interest in identifying and characterizing proteolytic enzymes capable of destroying ECM. One family of such proteinases, known as the matrix-degrading metalloproteinases (MMP), has been implicated in ECM destruction by virtue of their ability to degrade the proteinaceous components of ECM. In this application, a new metalloproteinase (CA-MMP/MMP23) is described to share only the catalytic domain with MMPs, but with its own distinct pro- and carboxyl- domains, thus representing a potentially new subfamily of the MMP superfamily. Notably, this new gene contains a type II transmembrane domain, lacks a classic cysteine-switch for latency and possesses a novel cysteine-array and Ig-like domain at its C-terminus. Thus, they hypothesize that CA-MMP is synthesized and displayed on cell membrane as a type II membrane proteinase, converted into soluble and active form by furin in the transGolgi network, and utilized by cells to degrade protein substrates as specified by its Cys-array (CA) domain and the immunoglobulin fold. To test this hypothesis, the following specific aims will be pursued: 1) Establish CA-MMP as the first MMP with a type II transmembrane anchor and characterize furin as its secretase, 2) Define the latency mechanism of CA-MMP, and 3) Establish CA-MMP as a unique proteolytic enzyme which can interact with novel protein partners via its C-terminal domains. Knowledge from these three approaches will ultimately contribute to our understanding of CA-MMP in pathophysiological process involving ECM remodeling and enhance our ability to fight degenerative diseases associated with ECM.