Browsing by Author "Teixeira, Douglas E."

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    SARS-CoV-2 spike protein inhibits megalin-mediated albumin endocytosis in proximal tubule epithelial cells
    (2022) Silva-Aguiar, Rodrigo P.; Teixeira, Douglas E.; Peruchetti, Diogo B.; Florentino, Lucas S.; Peres, Rodrigo A. S.; Gomes, Carlos P.; Marzolo, Maria-Paz; Rocco, Patricia M. R.; Pinheiro, Ana Acacia S.; Caruso-Neves, Celso
    Patients with COVID-19 have high prevalence of albuminuria which is used as a marker of progression of renal disease and is associated with severe COVID-19. We hypothesized that SARS-CoV-2 spike protein (S protein) could modulate albumin handling in proximal tubule epithelial cells (PTECs) and, consequently contribute to the albuminuria observed in patients with COVID-19. In this context, the possible effect of S protein on albumin endocytosis in PTECs was investigated. Two PTEC lines were used: HEK-293A and LLC-PK1. Incubation of both cell types with S protein for 16 h inhibited albumin uptake at the same magnitude. This effect was associated with canonical megalin-mediated albumin endocytosis because: (1) DQ-albumin uptake, a marker of the lyso-somal degradation pathway, was reduced at a similar level compared with fluorescein isothiocyanate (FITC)-albumin uptake; (2) dextran-FITC uptake, a marker of fluid-phase endocytosis, was not changed; (3) cell viability and proliferation were not changed. The inhibitory effect of S protein on albumin uptake was only observed when it was added at the luminal membrane, and it did not involve the ACE2/Ang II/AT1R axis. Although both cells uptake S protein, it does not seem to be required for modulation of albumin endocytosis. The mechanism underlying the inhibition of albumin uptake by S protein encompasses a decrease in megalin expression without changes in megalin trafficking and stability. These results reveal a possible mechanism to explain the albu-minuria observed in patients with COVID-19.
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    Surface megalin expression is a target to the inhibitory effect of bradykinin on the renal albumin endocytosis
    (2021) Alves, Sarah A. S.; Florentino, Lucas S.; Teixeira, Douglas E.; Silva-Aguiar, Rodrigo P.; Peruchetti, Diogo B.; Oliveira, Ana Carolina; Scharfstein, Julio; Marzolo, Maria-Paz; Pinheiro, Ana Acacia S.; Caruso-Neves, Celso
    Megalin-mediated albumin endocytosis plays a critical role in albumin reabsorption in proximal tubule (PT) epithelial cells (PTECs). Some studies have pointed out the modulatory effect of bradykinin (BK) on urinary protein excretion, but its role in PT protein endocytosis has not yet been determined. Here, we studied the possible correlation between BK and albumin endocytosis in PT. Using LLC-PK1 cells, a model of PTECs, we showed that BK specifically inhibited megalin-mediated albumin endocytosis. This inhibitory effect of BK was mediated by B2 receptor (B2R) because it was abolished by HOE140, an antagonist of B2R, but it was not affected by Lys-des-Arg(9)-BK, an antagonist of B1. BK induced the stall of megalin in EEA1(+) endosomes, but not in LAMP1(+) lysosomes, leading to a decrease in surface megalin expression. In addition, we showed that BK, through B2R, activated calphostin C-sensitive protein kinase C, which mediated its effect on the surface megalin expression and albumin endocytosis. These results reveal an important modulatory mechanism of PT albumin endocytosis by BK, which opens new possibilities to understanding the effect of BK on urinary albumin excretion.