Biology subjects

Grieve, A. G.

Publications and source records attributed to Grieve, A. G..

6 recordsLinked to original sources

bioRxiv2026

The unhindered lateral mobility of a rhomboid intramembrane protease enables synapse remodelling

Synapses must maintain their stable molecular organisation while retaining the capacity to remodel in response to changing demands. In order to flexibly change synaptic strength, the abundance of trans-synaptic adhesion complexes needs to be modulated, yet how this is achieved is poorly understood. Here, we identify the rhomboid protease RHBDL2 as a membrane-immersed regulator of adhesion complexes that enables mature synapses to adjust their composition both at steady-state and during their active restructuring. To do so, RHBDL2 possesses unrestrained diffusion properties that enable it to constitutively scan the neuronal surface and remove available adhesion molecules through irreversible cleavage of their transmembrane domains. Demonstrating its physiological importance, diffusion-dependent membrane surveillance by RHBDL2 is required for synapses to undergo remodelling during long term depression. Overall, we reveal a mechanism that cells use to preserve functional signalling complexes in membranes while selectively removing dispensable transmembrane proteins.

neuroscience↗

bioRxiv2026

Benchmarking AI-generated structural ensembles of membrane proteins against physics-based modelling

Proteins dynamically switch between a continuum of interconverting conformational states, and understanding these structural dynamics is important for understanding protein function and for developing therapeutics. Molecular dynamics (MD) simulations can provide insight into protein conformational ensembles, but sampling rare conformational states can require substantial computational resources. The recent development of AI-based approaches for generating protein conformational ensembles, such as the Biomolecular Emulator (BioEmu), offers a potential alternative, although it remains unclear whether these approaches can accurately capture the conformational landscapes, especially for special cases such as membrane proteins. Here, we assess the ability of BioEmu to model the conformational dynamics of a model membrane protein, the bacterial rhomboid intramembrane proteases GlpG. We find that BioEmu generates a range of conformations corresponding to both open and closed states of the rhomboid lateral gate, including states associated with different stages of the catalytic cycle. These conformations broadly correspond to states sampled during microsecond-timescale MD simulations, although BioEmu does not reproduce the full conformational landscape observed using MD. BioEmu also samples substantial conformational heterogeneity within the soluble domains of rhomboids, which are highly flexible and poorly represented in experimental structures. Overall, our findings demonstrate that BioEmu can generate plausible conformational ensembles for relatively large, six-and seven-pass membrane proteins, sampling rare states at a fraction of the computational cost of conventional MD simulations. These results suggest that AI-based ensemble generation could provide an accessible approach for exploring membrane protein dynamics and complement conventional molecular modelling approaches.

biophysics↗

bioRxiv2025

Structural and energetic insights into human rhomboid proteases reveal a unique lateral gating mechanism for orphan family members

Rhomboid proteases play fundamental roles in human biology and disease by cleaving substrate transmembrane domains. However, the absence of structural data and the inability to identify substrates for orphan human rhomboids limit mechanistic understanding. Lateral gating is considered the primary route by which transmembrane substrates access the rhomboid active site, although this has been demonstrated directly only for the bacterial rhomboid GlpG. To address this, we characterised the structures, conformational ensembles, and energy landscapes of human rhomboid proteases using AI-based structural models and molecular dynamics simulations, benchmarked by simulations seeded with GlpG crystal structures and models. We find that while some human rhomboids readily transition to open conformations compatible with transmembrane substrate access, orphan rhomboids possess unusually narrow lateral gates that require substantially higher energy to open. Our results reveal unexpected diversity in substrate engagement mechanisms among human rhomboids, and provide a rationale for the orphan status of recently evolved family members.

biochemistry↗

bioRxiv2021

iRhom2 regulates ERBB signalling to promote KRAS-driven oncogenesis

Dysregulation of the ERBB/EGFR signalling pathway causes multiple types of cancer (1, 2). Accordingly, ADAM17, the primary shedding enzyme that releases and activates ERBB ligands, is tightly regulated. It has recently become clear that iRhoms, inactive members of the rhomboid-like superfamily, are regulatory cofactors for ADAM17 (3, 4). Here we show that oncogenic KRAS mutants target the cytoplasmic domain of iRhom2 to induce ADAM17-dependent shedding and the release of ERBB ligands. Activation of ERK1/2 by oncogenic KRAS induces the phosphorylation of iRhom2, recruitment of the phospho-binding 14-3-3 proteins, and consequent ADAM17-dependent shedding of ERBB ligands. In addition, cancer-associated mutations in iRhom2 act as sensitisers in this pathway by further increasing KRAS-induced shedding of ERBB ligands. This mechanism is conserved in lung cancer cells, where iRhom activity is required for tumour xenograft growth. In this context, the activity of oncogenic KRAS is modulated by the iRhom2-dependent release of ERBB ligands, thus placing iRhom2 as a central component of a positive feedback loop in lung cancer cells. Overall, the cytoplasmic domain of iRhom2 is a critical component of KRAS-induced oncogenesis of lung cancer cells. Both ADAM17 and iRhom2 have also been implicated in a wide range of other cancers (5-10), so the mechanism we have revealed may also have wider oncogenic significance.

cancer biology↗

bioRxiv2020

Conformational surveillance of Orai1 by a rhomboid intramembrane protease prevents inappropriate CRAC channel activation

Calcium influx through plasma membrane calcium release-activated calcium (CRAC) channels, which are formed of hexamers of Orai1, is a potent trigger for many important biological processes, most notably in T cell mediated immunity. Through a bioinformatics-led cell biological screen, we have identified Orai1 as a substrate for the rhomboid intramembrane protease, RHBDL2. We show that RHBDL2 prevents stochastic signalling in unstimulated cells through conformational surveillance and cleavage of inappropriately activated Orai1. A conserved, disease-linked proline residue is responsible for RHBDL2 recognising only the active conformation of Orai1, and cleavage by RHBDL2 is required to sharpen switch-like signalling triggered by store-operated calcium entry. Loss of RHBDL2 control of Orai1 causes severe dysregulation of CRAC channel effectors including transcription factor activation, inflammatory cytokine expression and T cell activation. We propose that this seek-and-destroy function may represent an ancient activity of rhomboid proteases in degrading unwanted signalling proteins.

biochemistry↗

bioRxiv2018

FRMD8 promotes inflammatory and growth factor signalling by stabilising the iRhom/ADAM17 sheddase complex

Many intercellular signals are synthesised as transmembrane precursors that are released by proteolytic cleavage ( shedding) from the cell surface. ADAM17, a membrane-tethered metalloprotease, is the primary shedding enzyme responsible for the release of the inflammatory cytokine TNF and several EGF receptor ligands. ADAM17 exists in complex with the rhomboid-like iRhom proteins, which act as cofactors that regulate ADAM17 substrate shedding. Here we report that the poorly characterised FERM domain-containing protein FRMD8 is a new component of iRhom2/ADAM17 sheddase complex. FRMD8 binds to the cytoplasmic N-terminus of iRhoms, and is necessary to stabilise the iRhoms and ADAM17 beyond the Golgi. In the absence of FRMD8, iRhom2 and ADAM17 are degraded via the endolysosomal pathway, resulting in the reduction of ADAM17-mediated shedding. We have confirmed the pathophysiological significance of FRMD8 in iPSC-derived human macrophages and mouse tissues, thus demonstrating its role in the regulated release of multiple cytokine and growth factor signals.

biochemistry↗