RESUMO
Protein tyrosine phosphatase 1B (PTP1B, also known as PTPN1) is an established regulator of cell-matrix adhesion and motility. However, the nature of substrate targets at adhesion sites remains to be validated. Here, we used bimolecular fluorescence complementation assays, in combination with a substrate trapping mutant of PTP1B, to directly examine whether relevant phosphotyrosines on paxillin and focal adhesion kinase (FAK, also known as PTK2) are substrates of the phosphatase in the context of cell-matrix adhesion sites. We found that the formation of catalytic complexes at cell-matrix adhesions requires intact tyrosine residues Y31 and Y118 on paxillin, and the localization of FAK at adhesion sites. Additionally, we found that PTP1B specifically targets Y925 on the focal adhesion targeting (FAT) domain of FAK at adhesion sites. Electrostatic analysis indicated that dephosphorylation of this residue promotes the closed conformation of the FAT 4-helix bundle and its interaction with paxillin at adhesion sites.
Assuntos
Fosfoproteínas , Proteína Tirosina Fosfatase não Receptora Tipo 1 , Junções Célula-Matriz/metabolismo , Proteínas do Citoesqueleto/metabolismo , Quinase 1 de Adesão Focal/genética , Quinase 1 de Adesão Focal/metabolismo , Proteína-Tirosina Quinases de Adesão Focal/metabolismo , Adesões Focais/metabolismo , Paxilina/genética , Paxilina/metabolismo , Fosfoproteínas/metabolismo , Fosforilação , Proteína Tirosina Fosfatase não Receptora Tipo 1/genética , Proteína Tirosina Fosfatase não Receptora Tipo 1/metabolismoRESUMO
Brown widow spider (BrWS) (Latrodectus geometricus) venom produces intense systemic reactions such as cramps, harsh muscle nociceptive, nauseas, vomiting and hypertension. The proposed pathogenic mechanisms resulting in these accidents have principally been damages occurring at the nervous system. However, it is suspected that there is also damage of the adrenal glands, as a result of the experimental animal's clinical manifestations, which developed symptoms compatible with acute adrenal insufficiency. We have currently found that the adrenal gland is damaged by this venom gland homogenates (VGH) producing severe alterations on cortex cells resulting in death by acute adrenal insufficiency. In general, the ultrastructural study on the glands of mice under transmission electronic microscopy observations showed alterations in the majority of the intracellular membranes within 3 to 24h. BrWSVGH also showed specific actions on extracellular matrix proteins such as fibronectin, laminin and fibrinogen. In addition, zymogram experiments using gelatin as substrates detected gelatinolytic activity. The molecular exclusion fractionation of crude BrWSVGH resulted in 15 fractions, of which F1 and F2 presented alpha/beta-fibrinogenase and fibronectinolytic activities. Fractions F6, F14 and F15 showed only alpha-fibrinogenase activity; in contrast, the gelatinolytic action was only observed in fraction F11. Only metalloproteinase inhibitors abolished all these proteolytic activities. Our results suggest that adrenal cortex lesions may be relevant in the etiopathogenesis of severe brown widow spider envenoming. To our knowledge, this is the first report on adrenal gland damages, fibrinogenolytic activity and interrelations with cell-matrix adhesion proteins caused by L.geometricus VGH. The venom of this spider could be inducing hemostatic system damages on envenomed patients.
Assuntos
Córtex Suprarrenal/efeitos dos fármacos , Hemostasia/efeitos dos fármacos , Picada de Aranha/etiologia , Venenos de Aranha/toxicidade , Córtex Suprarrenal/enzimologia , Córtex Suprarrenal/ultraestrutura , Animais , Moléculas de Adesão Celular/metabolismo , Junções Célula-Matriz/efeitos dos fármacos , Junções Célula-Matriz/metabolismo , Cromatografia em Gel , Eletroforese em Gel de Poliacrilamida , Proteínas da Matriz Extracelular/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Microscopia Eletrônica de Transmissão , Picada de Aranha/sangue , Picada de Aranha/enzimologia , Picada de Aranha/patologia , Venenos de Aranha/enzimologiaRESUMO
Here, we define the mechanism through which protein tyrosine phosphatase 1B (PTP1B) is targeted to cell-matrix adhesion sites. Green fluorescent protein (GFP)-labeled PTP1B bearing the substrate-trapping mutation D181A was found in punctate structures in lamellae. The puncta co-localized with focal adhesion kinase (FAK) and Src, and defined the distal tips of cell-matrix adhesion sites identified with paxillin and vinculin. PTP1B is largely associated with the external face of the endoplasmic reticulum (ER) and the puncta develop from ER projections over cell-matrix adhesion sites, a process dependent on microtubules. Deletion of the ER-targeting sequence resulted in cytosolic localization and altered the distribution of PTP1B at cell-matrix foci, whereas mutations disrupting interactions with Src homology 3 (SH3) domains, and the insulin and cadherin receptors had no effect. PTP1B recognizes substrates within forming adhesion foci as revealed by its preferential association with paxillin as opposed to zyxin-containing foci. Our results suggest that PTP1B targets to immature cell-matrix foci in newly forming lamellae by dynamic extensions of the ER and contributes to the maturation of these sites.