Title : Expression and Characterization of
Membrane-Type 4 Matrix Metalloproteinase (
MT4-MMP ) and its Different Forms in Melanoma
Abstract :
- BACKGROUND/AIMS: Membrane-type matrix metalloproteinases ( MT-MMPs ) are expressed on the cell surface and hydrolyze extracellular matrix components and signaling molecules by which they influence cancer cell migration and metastasis
- Two of the six known MT-MMPs are anchored to the plasma membrane via a GPI anchor, one of which is MT4-MMP
- Only little is known about MT4-MMP expression, synthesis, regulation and degradation
- METHODS: We analyzed several human cancer cell lines as well as tissue homogenates using Western blotting and quantitative PCR for the expression of MT4-MMP
- Organelles of SK- Mel-28 cells were separated using continuous Iodixanol gradients
- Glycosylation of the SK- Mel-28 protein was studied via glucosidases and site directed mutagenesis of the MT4-MMP cDNA prior to transfection
- RESULTS: We found the MT4-MMP highly expressed in human melanoma cell lines as well as skin and melanoma tissue samples
- Three forms of MT4-MMP with molecular masses of 45 kDa, 58 kDa and 69 kDa were detected
- Further, we demonstrate that the 58 kDa form is the mature protein in the cell membrane, while the 69 kDa form is its precursor found in intracellular compartments
- The 69 kDa forms are processed by furin cleavage in the Golgi apparatus
- Moreover, we identified Asn318 as the single N-glycosylation site of MT4-MMP
- CONCLUSION: We demonstrate the novel expression of MT4-MMP in melanocytic tissues and propose a precursor/product-relationship of the different forms of MT4-MMP in melanoma cells