RESUMEN
The urokinase-type plasminogen activator (uPA) and its receptor (uPAR) play an important role in extracellular matrix degradation and cell migration in the central nervous system (CNS). To investigate the role of the uPA/uPAR system in the pathophysiology of acquired immunodeficiency syndrome dementia complex (ADC), we measured soluble uPAR (suPAR) levels in cerebrospinal fluid (CSF) and plasma from human immunodeficiency virus (HIV)-1-infected patients and controls. CSF suPAR levels were significantly higher in HIV-1-infected patients than in controls and in patients with ADC or opportunistic CNS infections (CNS-OIs) than in neurologically asymptomatic patients, irrespective of HIV-1 disease stage. The highest levels of suPAR were found in patients with ADC, and among those with CNS-OIs in patients with cytomegalovirus encephalitis or cryptococcosis. Plasma suPAR levels were higher in HIV-1-infected patients than in controls and increased with HIV-1 disease stage regardless of the presence of CNS disease. In patients with ADC or CNS-OIs, CSF suPAR levels correlated with CSF HIV-1 RNA, but not with plasma suPAR concentrations. Highly active antiretroviral therapy was associated with a significant and parallel decrease of both CSF suPAR and HIV-1 RNA. In brain tissue from patients with HIV-1 encephalitis, uPAR was highly expressed by microglial and multinucleated giant cells staining positively for HIV-1. The overexpression of uPAR in the CNS of patients with ADC suggests that the uPA/uPAR system may contribute to the tissue injury and neuronal damage in this disease.
Asunto(s)
Complejo SIDA Demencia/metabolismo , VIH-1 , Receptores de Superficie Celular/biosíntesis , Activador de Plasminógeno de Tipo Uroquinasa/metabolismo , Complejo SIDA Demencia/sangre , Complejo SIDA Demencia/líquido cefalorraquídeo , Estudios Transversales , Humanos , Estudios Longitudinales , Enfermedades del Sistema Nervioso/sangre , Enfermedades del Sistema Nervioso/líquido cefalorraquídeo , Enfermedades del Sistema Nervioso/metabolismo , Receptores de Superficie Celular/sangre , Receptores del Activador de Plasminógeno Tipo Uroquinasa , Estadísticas no ParamétricasRESUMEN
The urokinase-type plasminogen activator receptor (uPAR) is involved in cell migration and tissue remodelling, as a receptor for pro-uPA, as a cell adhesion component, and in a soluble form as a chemoattractant.We have analyzed the presence and the molecular forms of uPAR and uPAR-fragments in urine of ovarian cancer patients in comparison with tumour tissue, ascites, and serum. Carcinoma tissue contained high levels of uPAR, but more abundantly the D2D3-fragment. Ascitic fluid contained similar ratio's of suPAR fragments as corresponding tumour tissue, but serum only contained intact suPAR. Interestingly, urine contained predominantly the uPAR-fragments D1 and D2D3, and the pattern of these fragments was different in cancer patients as compared to healthy individuals. To confirm the hypothesis that circulating and urinary suPAR and suPAR-fragments originate from the tumour tissue, the presence of human suPAR (fragments) was analyzed in mice xenografted with human tumours. Indeed, high levels of urinary D1 fragment were found in mice carrying a tumour displaying cleaved uPAR on the cell surface, but little or no D1 was found in the urine from mice carrying a tumour with full-length uPAR. Mouse serum contained only intact suPAR. Our data demonstrate that the enhanced levels of suPAR fragments in the urine of cancer patients is likely to originate from uPAR expressed in the tumour tissue. Considering the biological activities that uPAR fragments display, the level and typing of uPAR fragments in urine might therefore be clinically more relevant than the plain serum uPAR content.
Asunto(s)
Proteínas de Neoplasias/metabolismo , Neoplasias Ováricas/química , Fragmentos de Péptidos/orina , Receptores de Superficie Celular/metabolismo , Animales , Estudios de Casos y Controles , Femenino , Humanos , Ratones , Proteínas de Neoplasias/sangre , Proteínas de Neoplasias/orina , Trasplante de Neoplasias , Neoplasias Ováricas/sangre , Neoplasias Ováricas/orina , Fragmentos de Péptidos/sangre , Fragmentos de Péptidos/metabolismo , Receptores de Superficie Celular/análisis , Receptores del Activador de Plasminógeno Tipo Uroquinasa , Solubilidad , Trasplante HeterólogoRESUMEN
The urokinase-type plasminogen activator receptor (uPAR/CD87) is a glycosylphosphatidylinositol-anchored membrane protein with multiple functions in extracellular proteolysis, cell adhesion, cell migration and proliferation. We now report that cell surface uPAR dimerizes and that dimeric uPAR partitions preferentially to detergent-resistant lipid rafts. Dimerization of uPAR did not require raft partitioning as the lowering of membrane cholesterol failed to reduce dimerization and as a transmembrane uPAR chimera, which does not partition to lipid rafts, also dimerized efficiently. While uPA bound to uPAR independently of its membrane localization and dimerization status, uPA-induced uPAR cleavage was strongly accelerated in lipid rafts. In contrast to uPA, the binding of Vn occurred preferentially to raft- associated dimeric uPAR and was completely blocked by cholesterol depletion.