Biology subjects

Collins, M. K.

Publications and source records attributed to Collins, M. K..

6 recordsLinked to original sources

bioRxiv2026

Molecular Determinants of G Protein Subtype-Specific Coupling to the Angiotensin II Type 1 Receptor

Many G protein-coupled receptors (GPCRs) are capable of activating multiple heterotrimeric G protein subtypes. The angiotensin II type 1 receptor (AT1R) couples to both Gq and Gi family members, and the two families mediate distinct aspects of the effects of angiotensin II (AngII) on blood pressure and fluid balance. Previous work has pointed to fundamental differences in the strength and ligand-dependence of Gq versus Gi activation by AT1R. Here we resolve key aspects of the mechanisms underlying these subtype-specific patterns of G protein coupling to AT1R. Using cellular biosensors, we show that AT1R activates Gq more efficaciously than Gi. Leveraging mini-G proteins, engineered versions of G subunits that diverge only in the C-terminal 5 helix, we identify four residues dispersed throughout the 5 helix that are sufficient to account for these differences. We employ radioligand binding to demonstrate that subtype-specific differences originate at the level of allosteric coupling between ligand and transducer binding, and we use Systematic Protein Affinity Strength Modulation biosensors to show that Gq-specific residues in the 5 helix increase affinity for AngII-activated AT1R. We provide evidence that the 5 helix residue with the greatest effect on coupling makes interactions with AT1R intracellular loop 3 that were not resolved in a previously reported AT1R-Gq cryo-electron microscopy structure. These findings enhance our understanding of how AT1R differentially activates Gq and Gi and may ultimately guide pharmacological approaches to modulate certain G proteins downstream of AT1R and other GPCRs.

biochemistry↗

bioRxiv2026

Gut microbiota promote early-life digestive function in songbirds

The vertebrate digestive tract harbors complex microbial communities whose influences on phenotypes and fitness in non-model organisms remain poorly understood. Here, we show that colonization with gut microbiota is critical for digestive development and function in a non-model songbird, the House sparrow (Passer domesticus). We raised nestlings under sterile (axenic) conditions and compared them to nestlings reconstituted (conventionalized) with microbiota from adult sparrows. Conventionalization drove significant increases in villus length, crypt depth, goblet cell density, and mucosal thickness in the small intestine. Conventionalized nestlings also exhibited increased growth of several digestive organs and elevated circulating bile acid levels, including bacterial metabolites known to promote growth and lipid metabolism in vertebrates. These results reveal functions of songbird microbiota and establish axenic methods for non-model oviparous vertebrates.

microbiology↗

bioRxiv2022

Human immune and gut microbial parameters associated with inter-individual variations in COVID-19 mRNA vaccine-induced immunity

COVID-19 mRNA vaccines induce protective adaptive immunity against SARS-CoV-2 in most individuals, but there is wide variation in levels of vaccine-induced antibody and T-cell responses. However, factors associated with this inter-individual variation remain unclear. Here, using a systems biology approach based on multi-omics analyses of human blood and stool samples, we find that baseline expression of AP-1 transcription factors, FOS and ATF3, is inversely correlated with BNT162b2 mRNA vaccine-induced T-cell responses. FOS expression is associated with transcription modules related to baseline immunity, but it is negatively associated with those related to T-cell activation upon BNT162b2 mRNA stimulation. Interestingly, the gut microbial fucose/rhamnose degradation pathway is positively correlated with FOS and ATF3 expression and inversely correlated with BNT162b2-induced T-cell responses. Taken together, these results demonstrate that baseline expression of AP-1 genes, which is associated with the gut microbial fucose/rhamnose degradation pathway, is a key negative correlate of BNT162b2-induced T-cell responses.

immunology↗

bioRxiv2021

HIV-1 Nef and CycK:CDK13 antagonize SERINC5 for optimal viral infectivity

HIV-1 Nef antagonizes SERINC5 by redirecting this potent restriction factor to the endosomes and lysosomes for degradation. However, the precise mechanism remains unclear. Using affinity purification/mass spectrometry, we identified cyclin K and cyclin-dependent kinase 13 (CycK:CDK13) as a new Nef-associated kinase complex. CycK:CDK13 phosphorylates the serine at position 360 (S360) in SERINC5, which is required for Nef downregulation of SERINC5 from the cell surface and its counter activity of the SERINC5 antiviral activity. To understand the role of S360 phosphorylation, we created chimeric proteins between CD8 and SERINC5. Nef not only downregulates, but importantly, also binds to this chimera in a S360-dependent manner. Thus, S360 phosphorylation increases interactions between Nef and SERINC5 and initiates the destruction of SERINC5 by the endocytic machinery.

microbiology↗

bioRxiv2018

Characterisation of Antibody Interactions with the G Protein of Vesicular Stomatitis Virus Indiana Strain and Other Vesiculovirus G Proteins

Vesicular stomatitis virus Indiana strain G protein (VSVind.G) is the most commonly used envelope glycoprotein to pseudotype lentiviral vectors (LV) for experimental and clinical applications. Recently, G proteins derived from other vesiculoviruses (VesG), for example Cocal virus, have been proposed as alternative LV envelopes with possible advantages compared to VSVind.G. Well-characterised antibodies that recognise VesG will be useful for vesiculovirus research, development of G protein-containing advanced therapy medicinal products (ATMPs), and deployment of VSVind-based vaccine vectors. Here we show that one commercially available monoclonal antibody, 8G5F11, binds to and neutralises G proteins from three strains of VSV as well as Cocal, and Maraba viruses, whereas the other commercially available monoclonal anti-VSVind.G antibody, IE9F9, binds to and neutralises only VSVind.G. Using a combination of G protein chimeras and site-directed mutations, we mapped the binding epitopes of IE9F9 and 8G5F11 on VSVind.G. IE9F9 binds close to the receptor binding site and competes with soluble low-density lipoprotein receptor (LDLR) for binding to VSVind.G, explaining its mechanism of neutralisation. In contrast, 8G5F11 binds close to a region known to undergo conformational changes when the G protein moves to its post-fusion structure, and we propose that 8G5F11 cross-neutralises VesGs by inhibiting this.\n\nIMPORTANCEVSVind.G is currently regarded as the gold-standard envelope to pseudotype lentiviral vectors. However, recently other G proteins derived from vesiculoviruses have been proposed as alternative envelopes. Here, we investigated two anti-VSVind.G monoclonal antibodies for their ability to cross-react with other vesiculovirus G proteins, and identified the epitopes they recognise, and explored the mechanisms behind their neutralisation activity. Understanding how cross-neutralising antibodies interact with other G proteins may be of interest in the context of host-pathogen interaction and co-evolution as well as providing the opportunity to modify the G proteins and improve G protein-containing medicinal products and vaccine vectors.

microbiology↗

bioRxiv2018

TMEM16F activation by Ca2+ triggers plasmalemma expansion and directs PD-1 trafficking

TMEM16F, an ion channel gated by high cytoplasmic Ca2+, is required for cell surface phosphatidylserine exposure during platelet aggregation and T cell activation. Here we demonstrate in Jurkat T cells and HEK293 cells that TMEM16F activation triggers large-scale surface membrane expansion in parallel with lipid scrambling. Following TMEM16F mediated scrambling and surface expansion, cells undergo extensive membrane shedding. The membrane compartment that expands the cell surface does not involve endoplasmic reticulum or acidified lysosomes. Surprisingly, T cells lacking TMEM16F expression not only fail to expand surface membrane, but instead rapidly internalize membrane via massive endocytosis (MEND). The T cell co-receptor PD-1 is selectively shed when TMEM16F triggers membrane expansion, while it is selectively internalized in the absence of TMEM16F. Its participation in this trafficking is determined by its single transmembrane domain. Thus, we establish a fundamental role for TMEM16F as a regulator of Ca2+-activated membrane trafficking.

cell biology↗