RESUMO
Mouse mast cell protease-4 (mMCP-4) has been linked to autoimmune and inflammatory diseases, although the exact mechanisms underlying its role in these pathological conditions remain unclear. Here, we have found that mMCP-4 is critical in a mouse model of the autoimmune skin blistering disease bullous pemphigoid (BP). Mice lacking mMCP-4 were resistant to experimental BP. Complement activation, mast cell (MC) degranulation, and the early phase of neutrophil (PMN) recruitment occurred comparably in mMCP-4(-/-) and WT mice. However, without mMCP-4, activation of matrix metalloproteinase (MMP)-9 was impaired in cultured mMCP-4(-/-) MCs and in the skin of pathogenic IgG-injected mMCP-4(-/-) mice. MMP-9 activation was not fully restored by local reconstitution with WT or mMCP-4(-/-) PMNs. Local reconstitution with mMCP-4(+/+) MCs, but not with mMCP-4(-/-) MCs, restored blistering, MMP-9 activation, and PMN recruitment in mMCP-4(-/-) mice. mMCP-4 also degraded the hemidesmosomal transmembrane protein BP180 both in the skin and in vitro. These results demonstrate that mMCP-4 plays two different roles in the pathogenesis of experimental BP, by both activating MMP-9 and by cleaving BP180, leading to injury of the hemidesmosomes and extracellular matrix of the basement membrane zone.
Assuntos
Mastócitos/enzimologia , Penfigoide Bolhoso/enzimologia , Serina Endopeptidases/metabolismo , Pele/enzimologia , Animais , Autoantígenos/genética , Autoantígenos/metabolismo , Membrana Basal/enzimologia , Membrana Basal/patologia , Degranulação Celular/efeitos dos fármacos , Degranulação Celular/fisiologia , Modelos Animais de Doenças , Ativação Enzimática/efeitos dos fármacos , Ativação Enzimática/genética , Hemidesmossomos/enzimologia , Hemidesmossomos/genética , Hemidesmossomos/patologia , Humanos , Imunoglobulina G/toxicidade , Mastócitos/patologia , Metaloproteinase 9 da Matriz/genética , Metaloproteinase 9 da Matriz/metabolismo , Camundongos , Camundongos Knockout , Neutrófilos/enzimologia , Neutrófilos/patologia , Colágenos não Fibrilares/genética , Colágenos não Fibrilares/metabolismo , Penfigoide Bolhoso/induzido quimicamente , Penfigoide Bolhoso/genética , Penfigoide Bolhoso/patologia , Serina Endopeptidases/genética , Pele/patologia , Colágeno Tipo XVIIRESUMO
Migration of keratinocytes requires a regulated and dynamic turnover of hemidesmosomes (HDs). We and others have previously identified three serine residues on the integrin ß4 cytoplasmic domain that play a critical role in the regulation of HD disassembly. In this study we show that only two of these residues (Ser-1356 and Ser-1364) are phosphorylated in keratinocytes after stimulation with either PMA or EGF. Furthermore, in direct contrast to previous studies performed in vitro, we found that the PMA- and EGF-stimulated phosphorylation of ß4 is not mediated by PKC, but by ERK1/2 and its downstream effector kinase p90RSK1/2. EGF-stimulated phosphorylation of ß4 increased keratinocyte migration, and reduced the number of stable HDs. Furthermore, mutation of the two serines in ß4 to phospho-mimicking aspartic acid decreased its interaction with the cytoskeletal linker protein plectin, as well as the strength of α6ß4-mediated adhesion to laminin-332. During mitotic cell rounding, when the overall cell-substrate area is decreased and the number of HDs is reduced, ß4 was only phosphorylated on Ser-1356 by a distinct, yet unidentified, kinase. Collectively, these data demonstrate an important role of ß4 phosphorylation on residues Ser-1356 and Ser-1364 in the formation and/or stability of HDs.
