Biology subjects

Scollo, F.

Publications and source records attributed to Scollo, F..

3 recordsLinked to original sources

bioRxiv2024

Unraveling the GM1 specificity of Galectin-1 binding to lipid membranes

Galectin-1 (Gal-1) is a galactose-binding protein involved in various cellular functions. Gal-1s activity has been suggested to be connected to two molecular concepts, which are however lacking experimental proof: a) enhanced binding affinity of Gal-1 towards membranes containing monosialotetrahexosylganglioside (GM1) over disialoganglioside GD1a and b) cross-linking of GM1s by homodimers of Gal-1. We provide evidence about the specificity and the nature of Gal-1 interaction with model membranes containing GM1 or GD1a, employing a broad panel of fluorescence-based and label-free experimental techniques, complemented by atomistic biomolecular simulations. Our study demonstrates that Gal-1 binds indeed specifically to GM1, and not to GD1a, when embedded in membranes over a wide range of concentrations (i.e., 30 nM to 10 M). The apparent binding constant is about tens of micromoles. On the other hand, no evidence of Gal-1/GM1 cross-linking was observed. Our findings suggest that cross-linking does not result from sole interactions between GM1 and Gal-1, indicating that in a physiological context, additional triggers are needed, which shift the GM1/Gal-1 equilibria towards the membrane-bound homodimeric Gal-1. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=198 SRC="FIGDIR/small/614102v2_ufig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@c4ff01org.highwire.dtl.DTLVardef@141c82eorg.highwire.dtl.DTLVardef@1bd7c0borg.highwire.dtl.DTLVardef@11af49e_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2023

Can calmodulin bind to lipids of the cytosolic leaflet of plasma membranes?

Calmodulin (CaM) is a ubiquitous calcium-sensitive messenger in eukaryotic cells. It was previously shown that CaM possesses an affinity for diverse lipid moieties, including those found on CaM-binding proteins. These facts together with our observation that CaM accumulates in membrane-rich protrusions of HeLa cells upon increased cytosolic calcium, motivated us to perform a systematic search for unmediated CaM interactions with model lipid membranes mimicking the cytosolic leaflet of plasma membranes. A range of experimental techniques and Molecular Dynamics simulations proves unambiguously that CaM interacts with lipid bilayers in the presence of calcium ions. Lipids phosphatidylserine (PS) and phosphatidylethanolamine (PE) hold the key to CaM-membrane interactions. Calcium induces an essential conformational rearrangement of CaM, but its binding to the headgroup of PS also neutralizes the membrane negative surface charge. More intriguingly, PE plays a dual role - it forms hydrogen bonds with CaM, but also destabilizes the lipid bilayer to increase exposure of hydrophobic acyl chains to the interacting proteins. Our findings suggest that upon increased intracellular calcium concentration, CaM and the cytosolic leaflet of cellular membranes can be functionally connected.

biophysics↗

bioRxiv2022

No evidence for detectable direct effects of magnetic field on cellular autofluorescence

Dramatically increased levels of electromagnetic radiation in the environment have raised concerns over the potential health hazards of electromagnetic fields. Various biological effects of magnetic fields have been proposed. Despite decades of intensive research, the molecular mechanisms procuring cellular responses remain largely unknown. The current literature is conflicting with regards to evidence that magnetic fields affect functionality directly at cellular level. Therefore, a search for potential direct cellular effects of magnetic fields represents a cornerstone that may propose an explanation for potential health hazards associated with magnetic fields. Recently, it was postulated that autofluorescence of HeLa cells is magnetic field sensitive, relying on single-cell imaging kinetic measurements. Here, we explore the utility of this approach by undertaking a screen for magnetic sensitivity of cellular autofluorescence in statistically relevant numbers (90-107) of HeLa cells. We did not observe any changes in cellular autofluorescence decay, when a modulated magnetic field was applied. We present a number of arguments indicating weak points in the analysis of magnetic field effects based on the imaging of cellular autofluorescence decay. Our work indicates that new methods are required to elucidate the effects of magnetic fields at the cellular level.

cell biology↗