title: Nuclear matrix metalloproteinase-2 in the cardiomyocyte and the ischemic-reperfused heart.
abstract: Matrix metalloproteinases (MMPs) are zinc-dependent proteases involved in intra- and extra-cellular matrix remodeling resulting from oxidative stress injury to the heart. MMP-2 was the first MMP to be localized to the nucleus; however, its biological functions there are unclear. We hypothesized that MMP-2 is present in the nucleus under normal physiological conditions but increases during myocardial ischemia-reperfusion (I/R) injury-induced oxidative stress, proteolyzing nuclear structural proteins. Lamins are intermediate filament proteins that provide structural support to the nucleus and are putative targets of MMP-2. To identify lamin susceptibility to MMP-2 proteolysis, purified lamin A or B was incubated with MMP-2 in vitro. Lamin A, but not lamin B, was proteolysed by MMP-2 into an approximately 50kDa fragment, which was also predicted by in silico cleavage site analysis. Immunofluorescent confocal microscopy and subcellular fractionation showed MMP-2 both in the cytosol and nuclei of neonatal rat ventricular myocytes. Rat hearts were isolated and perfused by the Langendorff method aerobically, or subjected to I/R injury in the presence or absence of o-phenanthroline, an MMP inhibitor. Nuclear fractions extracted from I/R hearts showed increased MMP-2 activity, but not protein level. The level of troponin I, a known sarcomeric target of MMP-2, was rescued in I/R hearts treated with o-phenanthroline, demonstrating the efficacy of MMP inhibition. However, lamin A or B levels remained unchanged in I/R hearts. MMP-2 has a widespread subcellular distribution in cardiomyocytes, including a significant presence in the nucleus. The increase in nuclear MMP-2 activity seen during stunning injury here, indicates yet unknown biological actions, other than lamin proteolysis, which may require more severe ischemia to effect.
authors.affiliation: Department of Pharmacology, Cardiovascular Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada. Electronic address: baghirov@ualberta.ca.
authors.forename: Sabina
authors.initials: S
authors.lastname: Baghirova
authors.affiliation: Department of Pharmacology, Cardiovascular Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, Cardiovascular Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada. Electronic address: bryan.g.hughes@gmail.com.
authors.forename: Bryan G
authors.initials: BG
authors.lastname: Hughes
authors.affiliation: Department of Pharmacology, Cardiovascular Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, Cardiovascular Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada. Electronic address: poirier1@ualberta.ca.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Poirier
authors.affiliation: Department of Pharmacology, Cardiovascular Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, Cardiovascular Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada. Electronic address: marciayuri.k@gmail.com.
authors.forename: Marcia Y
authors.initials: MY
authors.lastname: Kondo
authors.affiliation: Department of Pharmacology, Cardiovascular Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; Department of Pediatrics, Cardiovascular Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada. Electronic address: richard.schulz@ualberta.ca.
authors.forename: Richard
authors.initials: R
authors.lastname: Schulz
mesh_terms: D000818:Animals; D042541:Intracellular Space / Q000378:metabolism; D034904:Lamin Type A / Q000378:metabolism; D034921:Lamin Type B / Q000378:metabolism; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D009200:Myocardial Contraction; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D032383:Myocytes, Cardiac / Q000378:metabolism*; D015530:Nuclear Matrix / Q000378:metabolism*; D021381:Protein Transport; D059748:Proteolysis; D051381:Rats
chemical_list: D034904:Lamin Type A; D034921:Lamin Type B; D020778:Matrix Metalloproteinase 2
keywords: Lamin; Matrix metalloproteinase-2; Myocardial ischemia; Nucleus; Proteolysis; Reperfusion