title: Interaction of clusterin and matrix metalloproteinase-9 and its implication for epithelial homeostasis and inflammation.
abstract: Uncontrolled increases of matrix metalloproteinase-9 (MMP-9) activity have been causally linked to epithelial barrier disruption and severe symptoms of inflammatory diseases such as dry eye (DE). The data presented here show that the anti-inflammatory, cytoprotective intracellular and extracellular chaperone protein clusterin (CLU) interacts with MMP-9 both inside and outside epithelial cells. CLU bound very strongly to active MMP-9, with an affinity constant K(D) of 2.63 nmol/L. Unexpectedly, CLU had a much higher affinity for pro-MMP-9 than for active MMP-9 or pro-MMP-2, requiring the N-terminal propeptide domain of pro-MMP-9. The significance of the interaction between CLU and MMP-9 was demonstrated by the observation that CLU prevents stress-induced MMP-9 aggregation and inhibits MMP-9 enzymatic activity. Furthermore, CLU inhibited MMP-9-mediated disintegration of the tight junction structure formed between human epithelial cells. Additionally, CLU inhibited enzymatic activities of MMP-2, MMP-3, and MMP-7. Treatment with proinflammatory cytokines, which are known to increase MMP-9 transcription under inflammatory conditions, reduced the expression of CLU in human epithelial cells. Similarly, in a mouse model of human DE, inflammatory stress depleted CLU in the ocular surface epithelium but allowed MMP-9 to prevail therein. The present results thus provide novel insights into previously unrecognized mechanisms by which CLU maintains fluid-epithelial interface homeostasis, thereby preventing the onset of inflammatory conditions, especially where MMP-9 is actively involved.
authors.affiliation: USC Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA. shinwuje@usc.edu
authors.forename: Shinwu
authors.initials: S
authors.lastname: Jeong
authors.forename: Dolena R
authors.initials: DR
authors.lastname: Ledee
authors.forename: Gabriel M
authors.initials: GM
authors.lastname: Gordon
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Itakura
authors.forename: Nitin
authors.initials: N
authors.lastname: Patel
authors.forename: Aaron
authors.initials: A
authors.lastname: Martin
authors.forename: M Elizabeth
authors.initials: ME
authors.lastname: Fini
mesh_terms: D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D051152:Clusterin / Q000378:metabolism* / Q000494:pharmacology; D016207:Cytokines / Q000502:physiology; D003890:Desiccation; D015536:Down-Regulation / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D004847:Epithelial Cells / Q000378:metabolism; D019573:Epithelium, Corneal / Q000378:metabolism; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007249:Inflammation / Q000378:metabolism*; D018836:Inflammation Mediators / Q000502:physiology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D061965:Matrix Metalloproteinase Inhibitors; D051379:Mice; D011480:Protease Inhibitors / Q000494:pharmacology; D011485:Protein Binding / Q000502:physiology; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D051152:Clusterin; D016207:Cytokines; D018836:Inflammation Mediators; D061965:Matrix Metalloproteinase Inhibitors; D011480:Protease Inhibitors; D011994:Recombinant Proteins; D020780:Matrix Metalloproteinase 9