Biology subjects

Palmulli, R.

Publications and source records attributed to Palmulli, R..

3 recordsLinked to original sources

bioRxiv2024

Tethered exosomes containing MT1-MMP contribute to extracellular matrix degradation during breast cancer progression

For cancer cells to escape from the primary tumor and metastasize, they must degrade and navigate through the extracellular matrix (ECM). The transmembrane protease MT1-MMP plays a key role in localized matrix degradation, and its overexpression promotes cancer invasion. In this study, we demonstrate that MT1- MMP is trafficked to the intraluminal vesicles of multivesicular endosomes, and subsequently released from cells on exosomes, a subtype of extracellular vesicle that can be retained to the surface of the originating cell by the anti-viral restriction factor, tetherin. While tetherin overexpression is linked to increased cell migration and invasion in various cancers, its role in these processes remains unclear. Our findings reveal that expression of tetherin by breast cancer cells promotes the retention of MT1-MMP-positive exosomes at their cell surface, while tetherin loss enhances exosome escape and impairs ECM degradation. Thus, tethered exosomes promote the retention of MT1-MMP at the surface of cells, aiding the degradation of the ECM and promoting cancer cell invasion.

cell biology↗

bioRxiv2021

SARS-CoV-2 spike downregulates tetherin to enhance viral spread

The antiviral restriction factor, tetherin, blocks the release of several different families of enveloped viruses, including the Coronaviridae. Tetherin is an interferon-induced protein that forms parallel homodimers between the host cell and viral particles, linking viruses to the surface of infected cells and inhibiting their release. We demonstrated that SARS-CoV-2 infection causes tetherin downregulation, and that tetherin depletion from cells enhances SARS-CoV-2 viral titres. We investigated the potential viral proteins involved in abrogating tetherin function and found that SARS- CoV-2 ORF3a reduces tetherin localisation within biosynthetic organelles via reduced retrograde recycling and increases tetherin localisation to late endocytic organelles. By removing tetherin from the Coronavirus budding compartments, ORF3a enhances virus release. We also found expression of Spike protein caused a reduction in cellular tetherin levels. Our results confirm that tetherin acts as a host restriction factor for SARS-CoV-2 and highlight the multiple distinct mechanisms by which SARS-CoV-2 subverts tetherin function. Author SummarySince it was identified in 2019, SARS-CoV-2 has displayed voracious transmissibility which has resulted in rapid spread of the virus and a global pandemic. SARS-CoV-2 is a member of the Coronaviridae family whose members are encapsulated by a host-derived protective membrane shell. Whilst the viral envelope may provide protection for the virus, it also provides an opportunity for the host cell to restrict the virus and stop it spreading. The anti-viral restriction factor, tetherin, acts to crosslink viruses to the surface of infected cells and prevent their spread to uninfected cells. Here, we demonstrate that SARS-CoV-2 undergoes viral restriction by tetherin, and that SARS-CoV-2 moves tetherin away from the site of Coronavirus budding to enhance its ability to escape and infect naive cells. Tetherin depletion from cells enhanced SARS-CoV-2 viral release and increased propagation of the virus. We found that the SARS-CoV-2 protein, ORF3a, redirects tetherin away from the biosynthetic organelles where tetherin would become incorporated to newly forming SARS-CoV-2 virions - and instead relocalises tetherin to late endocytic organelles. We also found that SARS-CoV-2 Spike downregulates tetherin. These two mechanisms, in addition to the well described antagonism of interferon and subsequent ISGs highlight the multiple mechanisms by which SARS-CoV-2 abrogates tetherin function. Our study provides new insights into how SARS-CoV-2 subverts human antiviral responses and escapes from infected cells.

cell biology↗

bioRxiv2020

Specificities of exosome versus small ectosome secretion revealed by live intracellulartracking and synchronized extracellular vesicle release of CD9 and CD63

Despite their important and multiple roles in intercellular communications, the different populations of extracellular vesicles (EVs) and their secretion mechanisms are not fully characterized yet. In particular, how and to what extent EVs form either as intraluminal vesicles of endocytic compartments (exosomes), or at the plasma membrane (ectosomes) remains unclear. We followed in HeLa cells the intracellular trafficking of the EV markers CD9 and CD63 from the endoplasmic reticulum to their residency compartment and identified transient co-localization both at the plasma membrane (PM) and in endosomes, before they finally segregate. CD9 was more abundantly released in EVs than CD63. However, when forcing expression of CD63 at the PM, by mutating its lysosome-addressing motive, its secretion in EVs was increased. Thus, in HeLa cells, small ectosomes are more prominently released than exosomes. By comparative proteomic analysis, we identified a few surface proteins likely specific of either exosomes (e.g. LAMP1) or ectosomes (e.g. BSG, SLC3A2), based on their known intracellular location in lysosomes or the PM, and on the different effects on their release of Bafilomycin A1, a drug that neutralizes endosomal pH. Our work sets the path for molecular and functional discrimination of exosomes and small ectosomes in any cell type.

cell biology↗