Biology subjects

Hussain, H.

Publications and source records attributed to Hussain, H..

8 recordsLinked to original sources

bioRxiv2026

Lactate promotes IL-8 secretion in human alveolar macrophages through GPR132 and lipid metabolic reprogramming

Alveolar macrophages are the primary lung immune cell. They play a crucial role in both maintenance of tissue homeostasis and the initiation of inflammation, secreting multiple immune mediators including the chemokine interleukin-8 (IL-8). Inflammatory settings are often characterised by tissue hypoxia, increased glycolytic rates and lactate secretion, yet how lactate influences alveolar macrophage function remains unclear. Here we investigated how lactate, once considered a waste-product, shapes alveolar macrophage function. To do so, primary human alveolar macrophages (hAMs) and a combination of flow cytometry, ELISA/Luminex, western blot, light microscopy, bioluminescence resonance energy transfer (BRET) and analysis of publicly available datasets were used to understand the role of lactate in lung pathological environments. We demonstrate that hAMs sense extracellular lactate via the expression of different lactate transporters (e.g. MCT1, MCT4) and receptors (i.e. GPR132). Lactate treatment of hAMs increased IL-8 secretion in a MCT1-dependent manner. Lipid metabolism and lipid droplet formation, as well as direct lactate-driven GPR132 signalling were required for lactate-dependent IL-8 release. Our findings uncover a previously unrecognised dual mechanism by which lactate orchestrates immune regulation in hAMs. Specifically, lactate-driven IL-8 production requires two distinct lactate-driven processes: uptake via MCT1, which reprograms lipid metabolism, and signaling through the lactate receptor GPR132. This functional integration of lactate transport and receptor-mediated signaling provides new mechanistic insight into lactates role in hAM biology and highlights potential targets for therapeutic intervention.

immunology↗

bioRxiv2025

Machine Learning Guided Structure Activity Discovery of Polymer Configurations in Lipid Nanoparticles for Kiss-and-Run Endosomal Escape

Endosomal escape remains a major barrier to effective nucleic acid delivery via lipid nanoparticles (LNPs). Here, we address this challenge by incorporating a pH-sensitive polymer, polyhistidine, into LNPs (pLNPs) to facilitate endosomal escape, with a focus on optimizing the polymers molecular weight (MW) and configuration--parameters that remain largely unexplored. Through systematic engineering, we designed linear and branched polyhistidine architectures with varied MWs and configurations. In vivo screening identified an optimized pLNP formulation incorporating a symmetrical bis-lysine histidine dendron with a MW of [~]1800 g/mol, which achieved a 266-fold increase in liver bioluminescence following intravenous delivery of luciferase mRNA compared to standard LNPs at an equivalent RNA dose. Mechanistic studies revealed that polymer configuration within pLNPs is critical for eliciting the proton sponge effect, leading to osmotic swelling and endosomal rupture. This configuration also promoted rapid endosomal membrane destabilization via a kiss-and-run mechanism, enabling efficient cytosolic release. When delivering base editor mRNA and single-guide RNA, the optimized pLNPs achieved 8% gene editing efficiency in the mouse liver at a low dose of 0.1 mg/kg, compared to 1% with standard LNPs. To accelerate discovery and address macromolecular design challenges, we developed a machine learning (ML) framework based on amino acid-level graph neural networks (GNNs). This approach identified branched, dendritic configurations with densely arranged histidine residues on a multivalent core as key determinants of delivery performance. The top ML-predicted candidate, NS535, achieved a 705-fold increase in liver bioluminescence over standard LNPs, validating our data-driven design strategy. Together, these findings establish a closed-loop platform integrating rational design, mechanistic validation, and ML-guided optimization to advance RNA delivery. By elucidating structure-activity relationships for polyhistidine carriers and demonstrating efficient, low-dose genome editing, this work provides a blueprint for next-generation nucleic acid therapeutics.

bioengineering↗

bioRxiv2025

Molecular determinants of species-specific cell-cell recognition activating the class II gamete fusogen HAP2

Species-specific adhesion of complementary gametes is a prerequisite to cell fusion during fertilization. Despite its importance, the molecular mechanism underlying cell-cell recognition and membrane adhesion to drive gamete fusion is not fully understood for any organism. In the alga, Chlamydomonas, the species-specific gamete adhesion protein MAR1 guides the fusogen HAP2 into a pre-fusion conformation on mt- gametes and serves as a receptor for the FUS1 adhesion protein on mt+ gametes. Here, we show that soluble recombinant MAR1 completely blocks the HAP2-dependent gamete fusion process by binding to FUS1 on mt+ gametes and report the X-ray structure of the MAR1-FUS1 complex. In vivo gamete fusion experiments showed that mutations of key residues at the observed MAR1-FUS1 interface strongly impair adhesion, yet gamete fusion still proceeds, highlighting the efficiency of the fusion-activation process. These findings uncover the molecular architecture of a surface receptor complex whose formation releases the viral class II viral fusion-protein ortholog HAP2, allowing it to undergo its membrane-fusogenic conformational change.

cell biology↗

bioRxiv2024

Structure and physiological investigation of arginylated actin

Actin is an evolutionarily conserved cytoskeletal protein with crucial roles in cell polarity, division, migration, and muscle contraction. Actin function is regulated in part by posttranslational modifications. One such modification in non-muscle cells is arginylation, in which an arginine residue is added to the N-terminus of {beta}-actin. What is the structure of arginylated {beta}-actin (R-{beta}-actin), are its interactions with other proteins altered and what phenotypes result when R-{beta}-actin is the sole actin isoform present in the cell? Here we report the 4.2 [A] structure of ADP-bound human R-{beta}-actin filaments, the overall structure of which is nearly identical to the filaments made of non-arginylated actin. In vitro functional assays using isoform-pure actins with defined post-translational modifications reveal that the interaction between myosin-II and actin is altered upon actin arginylation, due to frequent detachment of myosin-II from R-actin filaments. In vivo, we find that replacement of the only actin gene in Schizosaccharomyces pombe with a synthetic gene encoding R-Sp-actin reduces Arp2/3-based actin patches while thickening the formin-induced actin. Furthermore, consistent with altered interactions between myosin-II and R-actin filaments, the assembly and constriction of cytokinetic actomyosin ring are perturbed in the R-Sp-actin cells. Thus, despite the overall structural similarity of arginylated and non-arginylated actin filaments, actin arginylation affects actin filament assortment into distinct subcellular structures and its interaction with myosin II.

biochemistry↗

bioRxiv2021

First high-quality genome assembly data of sago palm (Metroxylon sagu Rottboll)

The sago palm (Metroxylon sagu Rottboll) is a all-rounder palm, it is both a tropical halophytic starch-producing palm as well as an ornamental plant. Recently, a genome survey was conducted on this palm using Illumina sequencing platform but the BUSCO genome completeness is very low (21.5%) and most of them ([~]78%) are either fragmented or missing. Thus, in this study, the sago palm genome completeness was further improved with the utilization of the Nanopore sequencing platform that produced longer reads. A hybrid genome assembly was conducted and the outcome was a much complete sago palm genome with BUSCO completeness achieved at as high as 97.9% with only [~]2% of them either fragmented or missing. The estimated genome size of the sago palm is 509,812,790 bp in this study. A sum of 33,242 protein-coding genes were revealed from the sago palm genome and around 96.39% of them had been functionally annotated. An investigation on the carbohydrate metabolism KEGG pathways also unearthed that starch synthesis was one of the major sago palm activities. These data are indispensable for future molecular evolutionary and genome-wide association studies. Specifications Table O_TBL View this table: org.highwire.dtl.DTLVardef@1a2dc6aorg.highwire.dtl.DTLVardef@134e433org.highwire.dtl.DTLVardef@171efa9org.highwire.dtl.DTLVardef@12d6f26org.highwire.dtl.DTLVardef@1dc32a6_HPS_FORMAT_FIGEXP M_TBL C_TBL Value of the DataO_LIFirst complete genome dataset for the eco-economic important sago palm (Metroxylon sagu Rottboll). C_LIO_LIHigh completeness of sago palm genomic dataset will facilitate future researches, such as genome-wide association studies. C_LIO_LIThe data is useful in pioneering sago palm genetic landscape investigations which in turn unmask the mystery behind its high starch yield, salinity tolerance and disease resistance. C_LI

genomics↗

bioRxiv2021

Characterisation of the Ubiquitin-ESCRT pathway in Asgard archaea sheds new light on origins of membrane trafficking in eukaryotes

The ESCRT machinery performs a critical role in membrane remodelling events in all eukaryotic cells, including in membrane trafficking, membrane repair, cytokinetic abscission, in viral egress, and in the generation of extracellular vesicles. While the machinery is complex in modern day eukaryotes, where it comprises dozens of proteins, the system has simpler and more ancient origins. Indeed, homologues of ESCRT-III and the Vps4 ATPase, the proteins that execute the final membrane scission reaction, play analogous roles in cytokinesis and potentially in extracellular vesicle formation in TACK archaea where ESCRT-I and II homologues seem to be absent. Here, we explore the phylogeny, structure, and biochemistry of homologues of the ESCRT machinery and the associated ubiquitylation system found in genome assemblies of the recently discovered Asgard archaea. In these closest living prokaryotic relatives of eukaryotes, we provide evidence for the ESCRT-I and II sub-complexes being involved in the ubiquitin-directed recruitment of ESCRT-III,_as it is in eukaryotes. This analysis suggests a pre-eukaryotic origin for the Ub-coupled ESCRT system and a likely path of ESCRT evolution via a series of gene duplication and diversification events.

cell biology↗

bioRxiv2019

Pick-ya actin: A method to purify actin isoforms with bespoke key post-translational modifications

Actin is one of the most abundant eukaryotic cytoskeletal polymer-forming proteins, which in the filamentous form regulates a number of physiological processes, ranging from cell division and migration to development and tissue function. Actins are differentially post-translationally modified (PTMs) in different organisms, which include Met, Ala, Asp, and Glu N-acetylation, N-arginylation, and the 73th His residue (His-73) methylation, with different organisms displaying a distinct signature of PTMs. Currently methods are not available to produce actin isoforms with organism specific PTM profile. Here we report Pick-ya actin, a method to express actin isoforms from any eukaryote with its own key characteristic PTM pattern. We achieve this using a synthetic biology strategy in a yeast strain that expresses 1. actin isoforms with the desired N-end via ubiquitin fusion and 2. mammalian enzymes that promote acetylation and methylation. Pick-ya actin should greatly facilitate biochemical, structural, and physiological studies of the actin cytoskeleton and its PTMs.

cell biology↗

bioRxiv2018

Activation of intracellular transport by relieving KIF1C autoinhibition

The kinesin-3 KIF1C is a fast organelle transporter implicated in the transport of dense core vesicles in neurons and the delivery of integrins to cell adhesions. Here we report the mechanisms of autoinhibition and release that control the activity of KIF1C. We show that the microtubule binding surface of KIF1C motor domain interacts with its stalk and that these autoinhibitory interactions are released upon binding of protein tyrosine phosphatase PTPN21. The FERM domain of PTPN21 stimulates dense core vesicle transport in primary hippocampal neurons and rescues integrin trafficking in KIF1C-depleted cells. In vitro, human full-length KIF1C is a processive, plus-end directed motor. Its landing rate onto microtubules increases in the presence of either PTPN21 FERM domain or the cargo adapter Hook3 that binds the same region of KIF1C tail. This autoinhibition release mechanism allows cargo-activated transport and might enable motors to participate in bidirectional cargo transport without undertaking a tug-of-war.

cell biology↗