Biology subjects

Sahu, G.

Publications and source records attributed to Sahu, G..

4 recordsLinked to original sources

bioRxiv2026

L-type channel voltage-dependent facilitation results from asymmetric π-H and π-π quadrangle interactions at DI-DII domains

Voltage-dependent facilitation (VDF) is a unique phenomenon observed in L-type voltage-gated calcium (CaV) channels, in which depolarized prepulse voltages increase inward current by several fold, contributing to neuronal firing, neurotransmitter release, cardiac automaticity, and muscle contraction. Despite three decades of research, the molecular origin and biophysical mechanisms underlying VDF in L-type (CaV1.1-CaV1.4) channels remain elusive. A serendipitous observation that solutions stored in polypropylene tubes eliminated CaV1.2 and CaV1.3 L-type channel VDF led us to identify the leachable 2,4-di-tert-butylphenol (2,4-DTBP) as a selective VDF inhibitor. Docking and molecular dynamics simulations of 2,4-DTBP revealed a previously unreported {pi}-H and {pi}-{pi} interdomain quadrangle interaction, asymmetrically positioned at the DI-DII pore-domain (PD) interface of L-type channels. Point mutagenesis disrupted these quadrangle interactions and abolished the VDF, as confirmed by whole-cell and single-channel recordings of CaV1.2. Remarkably, introducing this {pi}-H and {pi}-{pi} quadrangle interaction into the DIIS6 segment of non-VDF-displaying CaV2.1 channels induced robust VDF. In conclusion, this study provides the first molecular evidence for the VDF endpoint: L-type channel-specific interdomain quadrangle interactions asymmetrically positioned at the DI-DII PD interface.

biophysics↗

bioRxiv2025

Lateral hypothalamus directs stress-induced modulation of acute and psoriatic itch

Stress and anxiety are well-known modulators of both physiological and pathological itch. Acute stress suppresses itch, while chronic stress exacerbates it. These effects are mediated by neural circuits within the brain, though the precise mechanisms remain poorly understood. In this study, we investigate the role of neurons in the stress-sensitive lateral hypothalamic area (LHA) in modulating itch. Using neural activity-dependent genetic labeling and chemogenetic tools, we selectively engaged a population of LHA neurons (LHAstress-TRAP neurons) responsive to stress. Transient stimulation of these neurons induced anxiety-like behaviors, conditioned place aversion, and suppressed acute (chloroquine-induced) and chronic (psoriatic) itch. Conversely, the inhibition of the LHAstress-TRAP neurons enhanced acute and chronic itch. Interestingly, LHAstress-TRAP neurons did not respond to acute itch stimuli, but their activity was temporally correlated with scratching episodes in mice with psoriasis. Ex vivo whole-cell patch-clamp recordings revealed that these neurons exhibit heightened excitability in psoriatic animals. Anterograde viral tracing demonstrated that LHAstress-TRAP neurons project to brainstem regions implicated in itch modulation, including the periaqueductal gray (PAG), rostral ventromedial medulla (RVM), and lateral parabrachial nucleus (LPBN). Furthermore, chemogenetic activation and optogenetic silencing of LHAstress-TRAP axon terminals revealed that bidirectional modulation of itch is primarily mediated through projections to the PAG. Together, these findings identify a previously unrecognized central mechanism by which stress modulates itch, centered on a specific population of LHA neurons and their downstream brainstem targets.

neuroscience↗

bioRxiv2024

Ion channels that mediate calcium-dependent control of spike patterns are spatially organized across the soma in relation to a cytoskeletal assembly

A spectrin-actin cytoskeleton defines the structure of axons and expression of ion channels that support spike propagation, but it is not known how calcium and potassium channels are organized at the soma to control spike output patterns. The hippocampal pyramidal cell slow afterhyperpolarization (sAHP) is generated by a CaRyK protein complex of Cav1.3 calcium, RyR2, and IK potassium channels reflecting an ER-PM junction. Super resolution imaging and dimension reduction identified a highly organized distribution of CaRyK protein clusters aligned as rows with [~]155 nm periodicity that extended to branchpoints to form a non-rigid lattice-like structure across the soma. All CaRyK proteins proved to align and colocalize with the polygonal spectrin {beta}II cytoskeleton. The data indicate that CaRyK proteins at ER-PM junctions that contribute to the sAHP to control the pattern of spike output are distributed with high precision as functional ion channel nodes across the somatic spectrin cytoskeletal network. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=120 HEIGHT=200 SRC="FIGDIR/small/607230v4_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@1a60adorg.highwire.dtl.DTLVardef@1c11894org.highwire.dtl.DTLVardef@34b50aorg.highwire.dtl.DTLVardef@59bb39_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2017

DNA-PK facilitates HIV transcription by regulating the activity of RNA polymerase II and the recruitment of transcription machinery at HIV LTR

Despite the use of highly effective antiretroviral therapy (HAART), the presence of latent or transcriptionally silent proviruses prevents cure and eradication of HIV infection. These transcriptionally silent proviruses are well protected from both the immune system and HAART regimens. Thus, in order to tackle the problem of latent HIV reservoirs, it is a prerequisite to define all the pathways that regulate HIV transcription. We have previously reported that DNA-PK facilitates HIV transcription by interacting with the RNA polymerase II (RNAP II) complex recruited at HIV LTR. To extend those studies further, here we demonstrate that DNA-PK promotes HIV transcription by supporting it at several stages, including initiation, pause-release and elongation. We discovered that DNA-PK increases phosphorylation of RNAP II C-terminal domain (CTD) at serine 5 (Ser5) and serine 2 (Ser2) by both directly catalyzing and by augmenting the recruitment of P-TEFb at HIV LTR. We found that DNA-PK facilitates the establishment of euchromatin structure at HIV LTR, which further supports HIV gene expression. DNA-PK inhibition or knockdown leads to the severe impairment of HIV gene expression and conversion of euchromatin to heterochromatin at HIV LTR. It also profoundly restricts HIV replication and reactivation of latent provirus. DNA-PK promotes the recruitment of TRIM28 at LTR and facilitates the release of paused RNAP II through TRIM28 phosphorylation. The results were reproduced in cell lines belonging to both lymphoid and myeloid lineages and were confirmed in primary CD4+ T cells and peripheral blood mononuclear cells (PBMCs) from HIV-infected patients.\n\nIMPORTANCEOur results reveal the important role of DNA-PK in supporting HIV transcription, replication and latent proviral reactivation. Intriguingly, this study sheds light on an important pathway that affects HIV gene expression. These findings provide strong rationale for developing and using transcriptional inhibitors, such as DNA-PK inhibitors, as supplement to HAART regimens in order to further enhance their effectiveness and to suppress toxicity due to HIV proteins.

molecular biology↗