The cytoplasmic carboxy-terminal amino acid determines the subcellular localization of proTGF-(alpha) and membrane type matrix metalloprotease (MT1-MMP).
Transforming growth factor alpha (TGF-(alpha)) is synthesized as a precursor transmembrane molecule (proTGF-(alpha)) whose ectodomain is shed from the cell surface generating mature, soluble, growth factor. In agreement with recent reports, here we show that the structural determinant that targets proTGF-(alpha) to the cell surface maps to the very C-terminal cytoplasmic amino acid, valine. The primary localization of proTGF-(alpha) C-terminal mutants is a perinuclear area that colocalizes with ER markers. Since the ectodomain shedding machinery that acts on proTGF-(alpha) is known to be located at the cell surface, deficient transport provides an explanation for the previously reported lack of PKC activated ectodomain shedding of proTGF-(alpha) C-terminal mutants. The transport of wild-type proTGF-(alpha) to the cell surface was found to be mediated by a mechanism that includes a specific component saturable by wild-type proTGF-(alpha) but not by cell surface transmembrane proteins whose trafficking is independent of their cytoplasmic tail such as betaglycan. C-terminal valines are likely to be a general determinant of the subcellular location of cell surface transmembrane proteins since the maturation and trafficking of MT1-MMP C-terminal mutants are severely impaired. Our data suggest the existence of a targeting mechanism that acts on cell surface transmembrane molecules as diverse as proTGF-(alpha) and MT1-MMP and that the interaction with such a mechanism depends on the identity of the C-terminal amino acid of the targeted molecules.
Laboratori de Recerca Oncològica, Servei d'Oncologia Médica, Hospital General Universitari Vall d'Hebron, Psg. Vall d'Hebron 119-129, Barcelona 08035, Spain.
J M
JM
Ureña
A
A
Merlos-Suárez
J
J
Baselga
J
J
Arribas
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D011509:Proteoglycans / Q000096:biosynthesis; D018125:Receptors, Transforming Growth Factor beta / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D014162:Transfection; D016211:Transforming Growth Factor alpha / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*
D011498:Protein Precursors; D011509:Proteoglycans; D018125:Receptors, Transforming Growth Factor beta; D011994:Recombinant Proteins; D016211:Transforming Growth Factor alpha; C052268:protransforming growth factor alpha; C071736:betaglycan; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases