Mechanisms for the control of matriptase activity in the absence of sufficient HAI-1.
Matriptase proteolytic activity must be tightly controlled for normal placental development, epidermal function, and epithelial integrity. Although hepatocyte growth factor activator inhibitor-1 (HAI-1) represents the predominant endogenous inhibitor for matriptase and the protein molar ratio of HAI-1 to matriptase is determined to be >10 in epithelial cells and the majority of carcinoma cells, an inverse HAI-1-to-matriptase ratio is seen in some ovarian and hematopoietic cancer cells. In the current study, cells with insufficient HAI-1 are investigated for the mechanisms through which the activity of matriptase is regulated. When matriptase activation is robustly induced in these cells, activated matriptase rapidly forms two complexes of 100- and 140-kDa in addition to the canonical 120-kDa matriptase-HAI-1 complex already described. Both 100- and 140-kDa complexes contain two-chain, cleaved matriptase but are devoid of gelatinolytic activity. Further biochemical characterization shows that the 140-kDa complex is a matriptase homodimer and that the 100-kDa complexes appear to contain reversible, tight binding serine protease inhibitor(s). The formation of the 140-kDa matriptase dimer is strongly associated with matriptase activation, and its levels are inversely correlated with the ratio of HAI-1 to matriptase. Given these observations and the likelihood that autoactivation requires the interaction of two matriptase molecules, it seems plausible that this activated matriptase homodimer may represent a matriptase autoactivation intermediate and that its accumulation may serve as a mechanism to control matriptase activity when protease inhibitor levels are limiting. These data suggest that matriptase activity can be rapidly inhibited by HAI-1 and other HAI-1-like protease inhibitors and "locked" in an inactive autoactivation intermediate, all of which places matriptase under very tight control.
Greenebaum Cancer Center, Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD 21201, USA.
Han
H
Xu
Zhenghong
Z
Xu
I-Chu
IC
Tseng
Feng-Pai
FP
Chou
Ya-Wen
YW
Chen
Jehng-Kang
JK
Wang
Michael D
MD
Johnson
Hiroaki
H
Kataoka
Chen-Yong
CY
Lin
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011487:Protein Conformation; D055503:Protein Multimerization; D053491:Proteinase Inhibitory Proteins, Secretory / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D004791:Enzyme Inhibitors; D007527:Isoenzymes; D053491:Proteinase Inhibitory Proteins, Secretory; C109149:SPINT1 protein, human; D012697:Serine Endopeptidases; C485595:matriptase