Biology subjects

Dalgarno, P. A.

Publications and source records attributed to Dalgarno, P. A..

3 recordsLinked to original sources

bioRxiv2022

OptoRheo: Simultaneous in situ micro-mechanical sensing and 3D imaging of live cell cultures

Biomechanical cues from the extracellular matrix (ECM) are essential for directing many cellular processes, from normal development and repair, to disease progression. To better understand cell-matrix interactions, we have developed a new instrument named OptoRheo that combines light sheet fluorescence microscopy with particle tracking microrheology. OptoRheo lets us image cells in 3D as they proliferate over several days while simultaneously sensing the mechanical properties of the surrounding extracellular and pericellular matrix at a sub-cellular length scale. OptoRheo can be used in two operational modalities (with and without an optical trap) to extend the dynamic range of microrheology measurements. We corroborated this by characterising the ECM surrounding live breast cancer cells in two distinct culture systems, cell clusters in 3D hydrogels and spheroids in suspension culture. This cutting-edge instrument will transform the exploration of drug transport through complex cell culture matrices and optimise the design of the next-generation of disease models.

bioengineering↗

bioRxiv2019

Unveiling the multi-step solubilization mechanism of single vesicles by detergents.

The solubilization of membranes by detergents is critical for many technological applications and has become widely used in biochemistry research to induce cell rupture, extract cell constituents, and to purify, reconstitute and crystallize membrane proteins. The thermodynamic details of solubilization have been extensively investigated, but the kinetic aspects remain poorly understood. Here we used a combination of single-vesicle Forster resonance energy transfer (svFRET), fluorescence correlation spectroscopy and quartz-crystal microbalance with dissipation monitoring to access the real-time kinetics and elementary solubilization steps of sub-micron sized vesicles, which are inaccessible by conventional diffraction-limited optical methods. Real-time injection of a non-ionic detergent, Triton X, induced biphasic solubilization kinetics of surface-immobilized vesicles labelled with the Dil/DiD FRET pair. The nanoscale sensitivity accessible by svFRET allowed us to unambiguously assign each kinetic step to distortions of the vesicle structure comprising an initial fast vesicle-swelling event followed by slow lipid loss and micellization. We expect the svFRET platform to be applicable beyond the sub-micron sizes studied here and become a unique tool to unravel the complex kinetics of detergent-lipid interactions.

biophysics↗

bioRxiv2017

A novel VPS33A interaction motif is a master-switch controlling the inhibition and promotion of mammalian Stx17 interactions with SNAP29 and VAMP7 during autophagy

Autophagosome clearance is accomplished by SNARE-mediated fusion of the vesicle membrane with the endolysosome. This must be carefully regulated to maintain the organisation of the membrane system and prevent mistargeted degradation. Here, we dissect the autophagosomal SNARE complex pathway and its regulation using FLIM-FRET as a readout of protein interaction in situ. We show that within the spatio-temporal framework of the cell, autophagosomal Stx17 preferentially heterodimerises with SNAP29, subsequently associating with VAMP7, not VAMP8 as currently believed. Additionally, we identify for the first time multi-modal regulation of SNARE assembly by the SM protein VPS33A, finding parallels and differences with other syntaxin-SM interactions and suggesting a unifying model of SM regulation. Contrary to current theory, the Stx17 N-peptide interacts in a positionally conserved, but mechanistically divergent manner with VPS33A, providing a late go, no-go step for autophagic fusion via a phosphoserine master-switch.

cell biology↗