title: The MAM (meprin/A5-protein/PTPmu) domain is a homophilic binding site promoting the lateral dimerization of receptor-like protein-tyrosine phosphatase mu.
abstract: The MAM (meprin/A5-protein/PTPmu) domain is present in numerous proteins with diverse functions. PTPmu belongs to the MAM-containing subclass of protein-tyrosine phosphatases (PTP) able to promote cell-to-cell adhesion. Here we provide experimental evidence that the MAM domain is a homophilic binding site of PTPmu. We demonstrate that the MAM domain forms oligomers in solution and binds to the PTPmu ectodomain at the cell surface. The presence of two disulfide bridges in the MAM molecule was evidenced and their integrity was found to be essential for MAM homophilic interaction. Our data also indicate that PTPmu ectodomain forms oligomers and mediates the cellular adhesion, even in the absence of MAM domain homophilic binding. Reciprocally, MAM is able to interact homophilically in the absence of ectodomain trans binding. The MAM domain therefore contains independent cis and trans interaction sites and we predict that its main role is to promote lateral dimerization of PTPmu at the cell surface. This finding contributes to the understanding of the signal transduction mechanism in MAM-containing PTPs.
authors.affiliation: Department of Enzymology, Institute of Biochemistry, Spl. Independentei 296, Bucharest 060031, Romania.
authors.forename: Valeriu B
authors.initials: VB
authors.lastname: Cismasiu
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Denes
authors.forename: Helmut
authors.initials: H
authors.lastname: Reiländer
authors.forename: Hartmut
authors.initials: H
authors.lastname: Michel
authors.forename: Stefan E
authors.initials: SE
authors.lastname: Szedlacsek
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D001665:Binding Sites; D002448:Cell Adhesion; D002460:Cell Line; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D018411:Spodoptera / Q000166:cytology; D008625:Tiopronin / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004220:Disulfides; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D008625:Tiopronin; C516862:PTPRN protein, human; D017027:Protein Tyrosine Phosphatases; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D003545:Cysteine