Novel intracellular role of matrix metalloproteinase-2 in cardiac cell injury

• Author / Creator

  Ali, Mohammad M. A.

• Despite originally being described as a secreted protease, matrix
  metalloproteinase‐2 (MMP‐2) was recently revealed to have targets within
  cardiomyocytes. The biological mechanism(s) that describes the intracellular localization
  of MMP‐2 is unknown and is thus the subject of this thesis. Additionally, activation and
  inhibition of MMP-2 as well as novel intracellular target(s) of it that are involved in
  cardiomyocyte injury were investigated.
  The cytosolic targeting of MMP-2 was examined and it was found that the signal
  sequence of MMP-2 led to its incomplete targeting to the endoplasmic reticulum for
  secretion. Moreover, an MMP-2 splice variant which lacks the signal sequence and is
  enriched in the cytosol was discovered. Thus, intracellular MMP-2 is explained by the
  expression of a splice variant and by the inefficient targeting of canonical MMP-2 to the
  secretory pathway.
  Intracellular MMP-2 was found to play a pathological role in myocardial
  ischemia/reperfusion injury by proteolyzing the giant sarcomeric protein, titin. Discrete
  co-localization between MMP-2 and titin was found at the sarcomeric Z-disc region.
  Isolated rat hearts subjected to ischemia/reperfusion injury showed cleavage of titin,
  whereas inhibition of MMP-2 prevented titin proteolysis and improved the contractile
  function.
  To explore whether oxidative stress affects intracellular MMP-2 activity, isolated
  cardiomyocytes were treated with various concentrations of hydrogen peroxide.
  Treatment with 200 μM hydrogen peroxide led to elevated MMP-2 level/activity in
  cardiomyocyte lysates. Hydrogen peroxide primarily caused necrotic and not apoptotic
  cell death, however, pretreatment with selective MMP inhibitors did not protect against
  necrosis.
  In myocardial ischemia/reperfusion injury, MMP-2 or calpain inhibitors were
  shown to improve the myocardial contractile function. In order to investigate whether
  calpain inhibitors target intracellular MMP-2, the inhibitory effect of some calpain
  inhibitors on MMP-2 activity was tested. The IC50 values of calpain inhibitors, PD-
  150606 and ALLN, against MMP-2 were determined to be 9.3 and 21.9 μM, respectively,
  revealing that some calpain inhibitors have significant pharmacological activity as
  inhibitors of MMP-2.
  In summary, these studies describe a set of mechanisms that cells utilize to
  equilibrate MMP-2 in both extracellular and intracellular locations. These results suggest
  that MMP-2 inhibitors should be rigorously tested as a therapeutic strategy to alleviate
  myocardial ischemia/reperfusion injury.

• Subjects / Keywords

  • Cell death
  • Matrix metalloproteinase-2
  • Cytosolic
  • Titin
  • Ischemia/reperfusion
  • Calpain inhibitors

• Graduation date

  Fall 2012

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3NK8N

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.