Biology subjects

Kusch, J.

Publications and source records attributed to Kusch, J..

5 recordsLinked to original sources

bioRxiv2026

Social anchors: how previous social locations shape current animal movement and habitat selection

Memory of past space use is an important factor in habitat selection, but memory of what? The concept of memory captures the geographic spaces that an animal has used in the past. There are, however, competing reasons why animals occupy a given space. Species may occupy space due to particular aspects of their memory. Using integrated step selection analysis, we tested the relative importance of memory: previous use of high forage quality or where social interactions occurred at two temporal scales in caribou (Ranger tarandus). The most important parameter to explain intra-seasonal movement was geographic memory. At the inter-annual scale, caribou more strongly revisited locations with high quality forage and where they had formed dyads with conspecifics. We posit that remembered locations of social fusion can function as social anchors. The effects of memory on movement behaviour depend upon the context, both social and resource-based, and not geographic space alone.

ecology↗

bioRxiv2025

Structural basis for gating inhibition by the cytoplasmic domain in HCN1 channels

Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels generate rhythmic electrical activity in cardiac and neuronal tissues, with isoform-specific cAMP sensitivity remaining poorly understood. While HCN2 exhibits strong cAMP regulation, HCN1 shows minimal response. To investigate the structural basis of this divergence, we analyzed two engineered HCN1 variants using cryo-electron microscopy. One variant (HCN112) incorporates the C-linker and CNBD from HCN2 into the HCN1 backbone and exhibited enhanced cAMP sensitivity, with structural analysis revealing a compressed cytoplasmic domain arrangement that may facilitate regulatory interactions. In contrast, the truncated HCN1{Delta}C variant (lacking the cytoplasmic domain) displayed an intermediately open pore conformation, supporting auto-inhibitory regulation by the CNBD in wild-type channels. These structural insights elucidate how domain-specific interactions modulate cAMP-dependent gating and intrinsic auto-inhibition, resolving long-standing questions about mechanistic divergence among HCN isoforms. Our findings not only shed new light on the structural mechanisms underlying isoform-specific cAMP sensitivity but also have implications for the development of therapeutic strategies targeting HCN channels in neurological and cardiac disorders. SIGNIFICANCE STATEMENTHyperpolarization-activated cyclic nucleotide-gated (HCN) channels are essential regulators of rhythmic electrical activity in the heart and brain, and their dysfunction is linked to disorders such as epilepsy, depression, and cardiac arrhythmias. Although HCN channel isoforms display highly divergent responses to cAMP modulation, the structural basis for these differences has remained elusive. This study reveals, through cryo-EM structures, how domain-specific interactions within the cytoplasmic regions of HCN1 channels underlie their unique gating and auto-inhibition properties, as well as their muted cAMP sensitivity compared to HCN2. These insights resolve long-standing mechanistic questions about HCN channel regulation and pave the way for rational design of targeted therapies that selectively modulate HCN isoform activity in neurological and cardiac disease.

biochemistry↗

bioRxiv2024

Subunit-specific conductance of single HCN pacemaker channels at femtosiemens resolution

Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are tetramers that generate rhythmic electrical activity in neuronal and cardiac pacemaker cells 1. The channels are activated by hyperpolarisation of the membrane voltage and additionally tuned by the second messenger cAMP at sympathetic stimulation. There are four mammalian isoforms, HCN1-4 2-4. The single-channel conductance,{gamma} , of HCN channels remains debated, with conflicting results ranging from near 1.5 pS for HCN2 5,6 to tens of pS for HCN1 7, HCN2 7 and HCN4 7,8, though the pore structure, viewed to determine the conductance 9,10, is either identical or highly conserved. To resolve this controversy, we analyzed all four mouse isoforms mHCN1-4 at femtosiemens resolution. We show that mHCN1, mHCN3 and mHCN4 also generate small conductance values, even smaller than that of mHCN2 with the sequence{gamma} mHCN2=1.54 pS >{gamma} mHCN1=0.84 pS >{gamma} mHCN3=0.54 pS {asymp}{gamma} mHCN4=0.51 pS. As shown by systematic mutagenesis and molecular dynamic simulations, the differences in the conductance are neither generated by the selectivity filter nor the inner gate 9, but by defined negative charges in the outer channel vestibule increasing cation occupation. In line with these results, heteromers of mHCN2 with either mHCN1, mHCN3 or mHCN4 lead to graded single-channel currents in-between those of the respective homomeric channels. Our approach at femtosiemens resolution provides insight into the function of recombinant and native HCN channels at the level of single subunits and is thus promising for the development of subunit-specific drugs acting on these clinically highly relevant channels 11.

physiology↗

bioRxiv2020

Functional and structural characterization of interactions between opposite subunits in HCN pacemaker channels

Hyperpolarization-activated and cyclic nucleotide (HCN) modulated channels are tetrameric cation channels. In each of the four subunits, the intracellular cyclic nucleotide-binding domain (CNBD) is coupled to the transmembrane domain via a helical structure, the C-linker. High-resolution channel structures suggest that the C-linker enables functionally relevant interactions with the opposite subunit, which might be critical for coupling the conformational changes in the CNBD to the channel pore. We combined mutagenesis, patch-clamp technique, confocal patch-clamp fluorometry, and molecular dynamics simulations to show that residue K464 of the C-linker is essential for stabilizing the closed state of the mHCN2 channel by forming interactions with the opposite subunit. MD simulations revealed that both cAMP and K464E induce a rotation of the intracellular domain relative to the channel pore, weakening the autoinhibitory effect of the unoccupied CL-CNBD region. The adopted poses are in excellent agreement with structural results.

biophysics↗

bioRxiv2020

Pathways of inter- and intrasubunit allosteric signaling in the C-linker disk and cyclic nucleotide-binding domain of HCN2 channels

Opening of hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels is controlled by membrane hyperpolarization and binding of cyclic nucleotides to the tetrameric cyclic nucleotide-binding domain (CNBD), attached to the C-linker disk (CL). Confocal patch-clamp fluorometry revealed a pronounced cooperativity of ligand binding among protomers. However, by which pathways allosteric signal transmission occurs remained elusive. Here, we investigate how changes in the structural dynamics of the CL- CNBD of mouse HCN2 upon cAMP binding relate to inter- and intrasubunit signal transmission. Applying a rigidity theory-based approach, we identify two intersubunit and one intrasubunit pathways that differ in allosteric coupling strength between cAMP binding sites or towards the CL. These predictions agree with results from electrophysiological and patch-clamp fluorometry experiments. Our results map out distinct routes within the CL-CNBD that modulate different cAMP binding responses in HCN2 channels. They signify that functionally relevant submodules may exist within and across structurally discernable subunits in HCN channels.

biophysics↗