The SARS-CoV-2 Spike protein mediates docking of the virus onto cells prior to viral invasion. Several cellular receptors facilitate SARS-CoV-2 Spike docking at the cell surface, of which ACE2 plays a key role in many cell types. The intermediate filament protein vimentin has been reported to be present at the surface of certain cells and act as a co-receptor for several viruses; furthermore, its potential involvement in interactions with Spike proteins has been proposed. Nevertheless, the potential colocalization of vimentin with Spike and its receptors on the cell surface has not been explored. Here we have assessed the binding of Spike protein constructs to several cell types. Incubation of cells with tagged Spike S or Spike S1 subunit led to discrete dotted patterns at the cell surface, which consistently colocalized with endogenous ACE2, but sparsely with a lipid raft marker. Vimentin immunoreactivity mostly appeared as spots or patches unevenly distributed at the surface of diverse cell types. Of note, vimentin could also be detected in extracellular particles and in the cytoplasm underlying areas of compromised plasma membrane. Interestingly, although overall colocalization of vimentin-positive spots with ACE2 or Spike was moderate, a selective enrichment of the three proteins was detected at elongated structures, positive for acetylated tubulin and ARL13B. These structures, consistent with primary cilia, concentrated Spike binding at the top of the cells. Our results suggest that a vimentin-Spike interaction could occur at selective locations of the cell surface, including ciliated structures, which can act as platforms for SARS-CoV-2 docking.

RESUMENObjetivo: Determinar la asociación entre depresión y dependencia funcional en pacientes adultos mayores del Centro Geriátrico Naval. Materiales y métodos: Estudio retrospectivo, transversal y analítico de un análisis secundario de base de datos, con un tamaño muestral por conveniencia de 625 adultos mayores. Resultados: En el análisis de regresión lineal de predicción de dependencia funcional según índice de Barthel, se encontró que, por cada punto obtenido en el cuestionario de Yesavage, disminuye en 4,8±1.82 puntos el índice de Barthel y, por 5 puntos, disminuye 29.99±3.62 puntos. En relación con el Índice de Lawton, se encontraron resultados significativos respecto a la edad, sexo, grado militar, rendimiento físico, fuerza de prensión y depresión. Conclusiones: Se evidenció asociación entre depresión y dependencia funcional para actividades básicas e instrumentales de la vida diaria. Asimismo, que a mayor riesgo de depresión, mayor probabilidad de presentar dependencia funcional según el índice de Barthel, independientemente de otras variables.Palabras Claves: Adulto mayor; depresión; discapacidad (Fuente: DeSC BIREME). Association between depression and functional dependence in elderly patientsABSTRACT Objective: To determine the association between depression and functional dependence in elderly patients of the Centro Geriátrico Naval (Peruvian naval medical center for elderly people). Materials and methods: A retrospective, cross-sectional, analytic study conducted from a secondary data analysis, with a convenience sample size of 625 elderly people. Results: In the linear regression analysis which predicts functional dependence according to the Barthel Index, it was found that, for each point in the Yesavage questionnaire, the Barthel Index score decreases 4.8±1.82 points and, for every 5 points, it decreases 29.99±3.62 points. In relation to the Lawton Index, significant outcomes were found regarding age, gender, military rank, physical performance, grip strength and depression. Conclusions:The results show an association between depression and functional dependence in performing basic and instrumental activities of daily life. Moreover, the higher the risk of depression, the higher the chance of developing functional dependence according to the Barthel Index, regardless of other variables.

The Spike protein from SARS-CoV-2 mediates docking of the virus onto cells and contributes to viral invasion. Several cellular receptors are involved in SARS-CoV-2 Spike docking at the cell surface, including ACE2 and neuropilin. The intermediate filament protein vimentin has been reported to be present at the surface of certain cells and act as a co-receptor for several viruses; furthermore, its potential involvement in interactions with Spike proteins has been proposed. Here we have explored the binding of Spike protein constructs to several cell types using low-temperature immunofluorescence approaches in live cells, to minimize internalization. Incubation of cells with tagged Spike S or Spike S1 subunit led to discrete dotted patterns at the cell surface, which showed scarce colocalization with a lipid raft marker, but consistent coincidence with ACE2. Under our conditions, vimentin immunoreactivity appeared as spots or patches unevenly distributed at the surface of diverse cell types. Remarkably, several observations including potential antibody internalization and adherence to cells of vimentin-positive structures present in the extracellular medium exposed the complexity of vimentin cell surface immunoreactivity, which requires careful assessment. Notably, overall colocalization of Spike and vimentin signals markedly varied with the cell type and the immunodetection sequence. In turn, vimentin-positive spots moderately colocalized with ACE2; however, a particular enrichment was detected at elongated structures positive for acetylated tubulin, consistent with primary cilia, which also showed Spike binding. Thus, these results suggest that vimentin-ACE2 interaction could occur at selective locations near the cell surface, including ciliated structures, which can act as platforms for SARS-CoV-2 docking.

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