title: The tetraspanin network modulates MT1-MMP cell surface trafficking.
abstract: The membrane-type 1 matrix metalloproteinase (MT1-MMP) drives fundamental physiological and pathophysiological processes. Among other substrates, MT1-MMP cleaves components of the extracellular matrix and activates other matrix-cleaving proteases such as MMP-2. Trafficking is a highly effective means to modulate MT1-MMP cell surface expression, and hence regulate its function. Here, we describe the complex interaction of MT1-MMP with tetraspanins, their effects on MT1-MMP intracellular trafficking and proteolytic function. Tetraspanins are credited as membrane organizers that form a network within the membrane to regulate the trafficking of associated proteins. In short, we found MT1-MMP to interact with the tetraspanin-associated EWI-2 protein by a yeast two-hybrid screen. Immunoprecipitation analysis confirmed this interaction and further revealed that MT1-MMP also stably interacts with distinct tetraspanins (CD9, CD37, CD53, CD63, CD81, and CD82) and the tetraspanin-like MAL protein. By using different MT1-MMP truncation constructs and mutants, we observed that all tetraspanins and MAL associated with the hemopexin domain of MT1-MMP. Moreover, this interaction was independent of O-glycosylation of MT1-MMP and exclusively occurred in the endoplasmic reticulum. Here, the respective subcellular compartment was identified by fitting the MT1-MMP interaction pattern to a model for post-translational processing of MT1-MMP. In addition, tetraspanins differentially affected the cell surface localization of MT1-MMP, its capacity to activate pro-MMP-2, and the collagen invasion capacity. Interestingly, the degree of tetraspanin-MT1-MMP association did not correlate with its impact on MT1-MMP function. Tetraspanins thus distinctly affect MT1-MMP subcellular localization and function, and may constitute an effective mechanism to control MT1-MMP-dependent proteolysis at the cell surface.
authors.affiliation: Institute of Physiology and Pathophysiology, Division of Cardiovascular Physiology, Heidelberg University, 69120 Heidelberg, Germany. h.schroeder@physiologie.uni-heidelberg.de
authors.forename: H M
authors.initials: HM
authors.lastname: Schröder
authors.forename: S C
authors.initials: SC
authors.lastname: Hoffmann
authors.forename: M
authors.initials: M
authors.lastname: Hecker
authors.forename: T
authors.initials: T
authors.lastname: Korff
authors.forename: T
authors.initials: T
authors.lastname: Ludwig
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D019556:COS Cells; D002462:Cell Membrane / Q000235:genetics / Q000473:pathology*; D002522:Chlorocebus aethiops; D004789:Enzyme Activation / Q000502:physiology; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism; D018093:Gelatinases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D053511:Matrix Metalloproteinase 14 / Q000235:genetics / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology; D059748:Proteolysis; D059470:Tetraspanins / Q000235:genetics / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; D004792:Enzyme Precursors; D059470:Tetraspanins; D018093:Gelatinases; C069860:progelatinase; C522361:MMP2 protein, human; D020778:Matrix Metalloproteinase 2; C507086:MMP14 protein, human; D053511:Matrix Metalloproteinase 14