title: A unique C-terminal domain allows retention of matrix metalloproteinase-27 in the endoplasmic reticulum.
abstract: Matrix metalloproteinase-27 (MMP-27) is poorly characterized. Sequence comparison suggests that a C-terminal extension (CTE) includes a potential transmembrane domain as in some membrane-type (MT)-MMPs. Having noticed that MMP-27 was barely secreted, we investigated its subcellular localization and addressed CTE contribution for MMP-27 retention. Intracellular MMP-27 was sensitive to endoglycosidase H. Subcellular fractionation and confocal microscopy evidenced retention of endogenous MMP-27 or recombinant rMMP-27 in the endoplasmic reticulum (ER) with locked exit across the intermediate compartment (ERGIC). Conversely, truncated rMMP-27 without CTE accessed downstream secretory compartments (ERGIC and Golgi) and was constitutively secreted. CTE addition to rMMP-10 (a secreted MMP) caused ER retention and blocked secretion. Addition of a PKA target sequence to the cytosolic C-terminus of transmembrane MT1-MMP/MMP-14 led to effective phosphorylation upon forskolin stimulation, but not for MMP-27, excluding transmembrane anchorage. Moreover, MMP-27 was protected from digestion by proteinase K. Finally, MT1-MMP/MMP-14 but neither endogenous nor recombinant MMP-27 partitioned in the detergent phase after Triton X-114 extraction, indicating that MMP-27 is not an integral membrane protein. In conclusion, MMP-27 is efficiently retained within the ER due to its unique CTE, which does not lead to stable membrane insertion. This could represent a novel ER retention system.
authors.affiliation: Cell Biology Unit, de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, Box B1.75.05, B-1200, Brussels, Belgium.
authors.forename: Antoine
authors.initials: A
authors.lastname: Cominelli
authors.forename: Mathias
authors.initials: M
authors.lastname: Halbout
authors.forename: Francisca
authors.initials: F
authors.lastname: N'Kuli
authors.forename: Pascale
authors.initials: P
authors.lastname: Lemoine
authors.forename: Pierre J
authors.initials: PJ
authors.lastname: Courtoy
authors.forename: Etienne
authors.initials: E
authors.lastname: Marbaix
authors.forename: Donatienne
authors.initials: D
authors.lastname: Tyteca
authors.forename: Patrick
authors.initials: P
authors.lastname: Henriet
mesh_terms: D000595:Amino Acid Sequence; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D006801:Humans; D020782:Matrix Metalloproteinases / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D020782:Matrix Metalloproteinases
keywords: ERGIC; Triton X-114; brefeldin A; intermediate compartment; intracellular MMP; membrane; proteinase K; surface biotinylation