Mechanisms of cytosolic targeting of matrix metalloproteinase-2.
Matrix metalloproteinase-2 (MMP-2) is best understood for its biological actions outside the cell. However, MMP-2 also localizes to intracellular compartments and the cytosol where it has several substrates, including troponin I (TnI). Despite a growing list of cytosolic substrates, we currently do not know the mechanism(s) that give rise to the equilibrium between intracellular and secreted MMP-2 moieties. Therefore, we explored how cells achieve the unique distribution of this protease. Our data show that endogenous MMP-2 targets inefficiently to the endoplasmic reticulum (ER) and shows significant amounts in the cytosol. Transfection of canonical MMP-2 essentially reproduces this targeting pattern, suggesting it is the quality of the MMP-2 signal sequence that predominantly determines MMP-2 targeting. However, we also found that human cardiomyocytes express an MMP-2 splice variant which entirely lacks the signal sequence. Like the fraction of ER-excluded, full-length MMP-2, this variant MMP-2 is restricted to the cytosol and specifically enhances TnI cleavage upon hypoxia-reoxygenation injury in cardiomyocytes. Together, our findings describe for the first time a set of mechanisms that cells utilize to equilibrate MMP-2 both in the extracellular milieu and intracellular, cytosolic locations. Our results also suggest approaches to specifically investigate the overlooked intracellular biology of MMP-2.
Department of Pharmacology, Cardiovascular Research Centre, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada.
Mohammad A M
MA
Ali
Ava K
AK
Chow
Arulmozhi D
AD
Kandasamy
Xiaohu
X
Fan
Lori J
LJ
West
Bryan D
BD
Crawford
Thomas
T
Simmen
Richard
R
Schulz
D015687:Cell Hypoxia / Q000502:physiology; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000378:metabolism; D014162:Transfection / Q000379:methods; D019210:Troponin I / Q000378:metabolism
D018076:DNA, Complementary; D019210:Troponin I; D020778:Matrix Metalloproteinase 2