Biology subjects

Lalioti, V.

Publications and source records attributed to Lalioti, V..

3 recordsLinked to original sources

bioRxiv2024

Key role of vimentin in the organization of the primary cilium

We previously reported the presence of the intermediate filament vimentin at the primary cilium of lung cancer epithelial cells. In this study we further demonstrate that vimentin is intimately intertwined with acetylated tubulin at this structure. Interestingly, although vimentin can be detected along the whole length of the primary cilium, phospho-serine 56 vimentin is found particularly enriched at its basal region in A549 lung cancer cells. Vimentin appears to play a pivotal role in ciliogenesis, since its depletion in MEF or in A549 cells results in a lower proportion of cells displaying primary cilia and recognizable basal bodies. Furthermore, the detectable cilia in vimentin depleted cells are shorter. In addition, the centriolar structure appears disrupted in vimentin deficient cells, as indicated by an abnormal distribution of {gamma}- and acetylated tubulin. Moreover, these cells display a defective organization of the pericentriolar material, characterized by a marked decrease in the levels of pericentrin and a diffuse distribution of Rab11. Taken together, our results show that vimentin is present at the primary cilium and suggest that it plays an important role in cilium structure and biogenesis, since its depletion leads to marked morphological defects and altered organization of key elements of this structure.

cell biology↗

bioRxiv2023

Vimentin cysteine 328 modifications finely tune network organization and influence actin remodeling under oxidative and electrophilic stress

Cysteine residues can undergo multiple posttranslational modifications with diverse functional consequences, potentially behaving as tunable sensors. The intermediate filament protein vimentin has important implications in pathophysiology, including cancer progression, infection, and fibrosis, and maintains a close interplay with other cytoskeletal structures, such as actin filaments and microtubules. We previously showed that the single vimentin cysteine, C328, is a key target for oxidants and electrophiles. Here, we demonstrate that structurally diverse cysteine-reactive agents, including electrophilic mediators, oxidants and drug-related compounds, disrupt the vimentin network eliciting morphologically distinct reorganizations. As most of these agents display broad reactivity, we pinpointed the importance of C328 by confirming that local perturbations introduced through mutagenesis provoke structure-dependent vimentin rearrangements. Thus, GFP-vimentin wild type (wt) forms squiggles and short filaments in vimentin-deficient cells, the C328F, C328W, and C328H mutants generate diverse filamentous assemblies, and the C328A and C328D constructs fail to elongate yielding dots. Remarkably, vimentin C328H structures resemble the wt, but are strongly resistant to electrophile-elicited disruption. Therefore, the C328H mutant allows elucidating whether cysteine-dependent vimentin reorganization influences other cellular responses to reactive agents. Electrophiles such as 1,4-dinitro-1H-imidazole and 4-hydroxynonenal induce robust actin stress fibers in cells expressing vimentin wt. Strikingly, under these conditions, vimentin C328H expression blunts electrophile-elicited stress fiber formation, apparently acting upstream of RhoA. Analysis of additional vimentin C328 mutants shows that electrophile-sensitive and assembly-defective vimentin variants permit induction of stress fibers by reactive species, whereas electrophile-resistant filamentous vimentin structures prevent it. Together, our results suggest that vimentin acts as a break for actin stress fibers formation, which would be released by C328-aided disruption, thus allowing full actin remodeling in response to oxidants and electrophiles. These observations postulate C328 as a "sensor" transducing structurally diverse modifications into fine-tuned vimentin network rearrangements, and a gatekeeper for certain electrophiles in the interplay with actin.

cell biology↗

bioRxiv2021

Immunolocalization studies of vimentin and ACE2 on the surface of cells exposed to SARS-CoV-2 Spike proteins

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.

cell biology↗