Biology subjects

Pedersen, P. A.

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

5 recordsLinked to original sources

bioRxiv2026

Glucose derived redox equivalents preserve PKA activity and glucagon secretion during hypoglycaemia

The release of glucagon from pancreatic alpha cells is a core component of hypoglycaemic counter regulation. Several mechanisms regulate glucagon release including paracrine control by neighbouring cell types, and changes in extracellular glucose. While the inhibitory effect of glucose on glucagon secretion is well established, the exact way in which glucose metabolism contributes to alpha cell function remains unclear. Here, we use live-cell imaging of the redox potential in alpha cells within intact islets to investigate whether non-mitochondrial glucose metabolism contributes to the potentiation of glucagon secretion at low glucose. Our findings show that increased glucose metabolism through the pentose phosphate pathway elevates the cytosolic redox potential in alpha cells. Using a combination of antioxidant treatment and pre-incubation in 5 mM glucose, we find that the cytosolic redox potential affects PKA activity in alpha cells and that changes in whole body redox state affects the counterregulatory response in mice. These findings indicate that prior glucose-driven redox potential charging is essential for maintaining glucagon secretion at low glucose.

physiology↗

bioRxiv2026

Long-term single-molecule Ca2+ flux recordings reveal mode-switching regulation of Ca2+-ATPases

Calcium (Ca{superscript 2}) is a universal second messenger that governs processes ranging from muscle contraction and secretion to gene expression and cell fate. Ca{superscript 2}-ATPases establish and maintain steep Ca{superscript 2} gradients across intracellular membranes, yet how regulatory inputs modulate the underlying single-pump Ca{superscript 2} currents has remained inaccessible. Here we develop a non-saturating, self-regenerating single-vesicle assay that monitors over hours the zeptoampere (10-{superscript 2}{superscript 1} A) currents produced by individual Ca{superscript 2}-ATPases. In parallel, we establish a workflow to record single-molecule currents from human sarco/endoplasmic reticulum Ca{superscript 2}-ATPases (hSERCA) in native endoplasmic reticulum vesicles. Using reconstituted LMCA1, a bacterial SERCA homologue, we observe stochastic switching between minute-long pumping and inactive modes, as well as uncoupled Ca{superscript 2} leakage events that are suppressed by vanadate. Extravesicular pH controls a previously unrecognized dormant pre-activation mode that delays the onset of pumping, without measurably altering pumping rates or active-mode lifetimes. Extending the assay to endogenous hSERCA reveals delayed activation and ultraslow pumping/inactive mode-switching without detectable transprotein Ca{superscript 2} leakage. ATP and Ca{superscript 2} regulate the probability of hSERCA activation by modulating dormant-mode occupancy. Together, these results extend ultraslow mode-switching, previously observed only for proton pumps, to Ca{superscript 2}-ATPases and identify probability-gated entry into productive cycling as a distinct regulatory axis of human Ca{superscript 2}-ATPase regulation that can modulate the timing and heterogeneity of Ca{superscript 2} store refilling without changing on-cycle kinetics.

biophysics↗

bioRxiv2025

Detergent-free reconstitution of transmembrane proteins in giant liposomes of complex curvature by the Synthetic Membrane Transfer

Transmembrane proteins perform many crucial functions in the cell, including transfer of matter and information across the membrane. Giant Unilamellar Vesicles (GUVs) are the ideal tool for studying these processes; yet functional transmembrane protein reconstitution in GUVs still represents a bottleneck in bottom-up synthetic biology. Here, we developed a novel approach that we call Synthetic Membrane Transfer (SMT), where transmembrane proteins reconstituted into styrene-maleic acid particles in a detergent-free environment can be transferred to the GUV membrane. The SMT approach is a one-step, facile and general method that works for structurally diverse proteins, and it does not require any specific lipid or buffer composition. Moreover, the SMT is fully compatible with the Synthetic Membrane Shaper (SMS) technology, which allows to deform GUVs in a controlled fashion, obtaining dumbbell-shaped GUVs exhibiting a catenoid-like geometry. The combination of SMT and SMS results in functional reconstitution of transmembrane proteins in catenoid membrane necks. Using this approach, we demonstrate that Mic10, a component of the MICOS complex, directly senses membrane curvature and localizes at the neck of dumbbells GUVs, a geometry that recapitulates the shape of mitochondria cristae junctions. This paves the way for bottom-up reconstitution of the MICOS complex on a physiological membrane geometry.

synthetic biology↗

bioRxiv2024

TMPRSS6 cleaves KCNE1 and causes arrhythmias in iron overload disease

Iron storage disease is associated with cardiovascular manifestations, including various forms of cardiac arrhythmias of unknown origin. In this study, cardiac arrhythmias associated with iron overload were investigated in human iPSC-derived cardiomyocytes (hiPSC-CM) and hiPSC-derived sinus node-like pacemaker cells. Among other effects, iron overload leads to an increase in the plasma membrane-anchored protease TMPRSS6. TMPRSS6 cleaves the auxiliary subunit KCNE1 N-terminally and thus modulates the function of both the IKs (KCNQ1/KCNE1 current) and the If (HCN4/KCNE1) ion channels. Furthermore, TMPRSS6 induces a reduction of electric field potential (EFP) count and increased duration in hiPSC-derived ventricular-like cells and in hiPSC-derived pacemaker-like cells. In accordance with these in vitro generated results, TMPRSS6-mediated interactions show pro-arrhythmic effects in silico. Therefore, the TMPRSS6 - KCNE1-KCNQ1 and TMPRSS6 - KCNE1-HCN4 cascades may represent new clinically relevant pro-arrhythmic mechanisms in iron overload diseases.

physiology↗

bioRxiv2020

Order and disorder - an integrative structure of the full-length human growth hormone receptor

Despite the many physiological and pathophysiological functions of the human growth hormone receptor (hGHR), a detailed understanding of its modus operandi is hindered by the lack of structural information of the entire receptor at the molecular level. Due to its relatively small size (70 kDa) and large content of structural disorder (>50%), this membrane protein falls between the cracks of conventional high-resolution structural biology methods. Here, we study the structure of the full-length hGHR in nanodiscs with small angle-X-ray scattering (SAXS) as the foundation. We developed an approach in which we combined SAXS, X-ray diffraction and NMR spectroscopy obtained on the individual domains and integrated the data through molecular dynamics simulations to interpret SAXS data on the full-length hGHR in nanodiscs. The structure of the hGHR was determined in its monomeric state and provides the first experimental model of any full-length cytokine receptor in a lipid membrane. Combined, our results highlight that the three domains of the hGHR are free to reorient relative to each other, resulting in a broad structural ensemble. Our work exemplifies how integrating experimental data from several techniques computationally, may enable the characterization of otherwise inaccessible structures of membrane proteins with long disordered regions, a widespread phenomenon in biology. To understand orchestration of cellular signaling by disordered chains, the hGHR is archetypal and its structure emphasizes that we need to take a much broader, ensemble view on signaling.

biophysics↗