Biology subjects

Scott, M. K.

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

3 recordsLinked to original sources

bioRxiv2026

ARMH3 acts as a central scaffold at the Golgi/TGN through interactions with Arl5, GBF1, and PI4KB

The armadillo repeat protein ARMH3 regulates the activity and localisation of the Golgi resident lipid kinase phosphatidylinositol 4 kinase III{beta} (PI4KB) and the Golgi-specific brefeldin A-resistance guanine nucleotide exchange factor 1 (GBF1) that activates Arf1. ARMH3 localises to the trans Golgi network (TGN) via the GTPase Arl5. We used hydrogen deuterium exchange mass spectrometry (HDX-MS) and AI-enabled modeling to define the interfaces of ARMH3 with its binding partners Arl5, PI4KB, and GBF1. The ARMH3-Arl5 interface was determined to consist of the N and C termini of ARMH3, with Arl5 binding causing conformational changes in ARMH3 located at a shared PI4KB/GBF1 interface. Both PI4KB and GBF1 form mutually exclusive complexes with ARMH3, with GBF1 binding to ARMH3 through a disordered loop we have named the ARMH3 binding region (ABR). The ARMH3 interfaces in PI4KB and GBF1 contain phosphosites, with the phosphomimetic mutation of GBF1 blocking complex formation. These findings provide new insights into the role of ARMH3 as a master coordinator of GTPase and phosphoinositide signaling at the Golgi/TGN.

biochemistry↗

bioRxiv2025

A Bitopic mTORC Inhibitor Reverses Neural Phenotypes in a Tuberous Sclerosis Complex Murine Model of SEGA-like Hamartomas

Neural stem cells (NSCs) of the ventricular-subventricular zone (V-SVZ) generate diverse cell types including striatal glia during the neonatal period. NSC progeny uncouple stem cell-related mRNA transcripts from being translated during differentiation. We previously demonstrated that Tsc2 inactivation, which occurs in the neurodevelopmental disorder Tuberous Sclerosis Complex (TSC), prevents this from happening. Loss of Tsc2 causes hyperactivation of the protein kinase mechanistic target of rapamycin complex 1 (mTORC1), altered translation, retention of stemness in striatal glia, and the production of misplaced cytomegalic neurons having hypertrophic dendrite arbors. These phenotypes model characteristics of TSC hamartomas called subependymal giant cell astrocytomas (SEGAs). mTORC1 inhibitors called rapamycin analogs (rapalogs) are currently used to treat TSC and to assess the role of mTORC1 in regulating TSC-related phenotypes. Rapalogs are useful for treating SEGAs. However, they require lifelong application, have untoward side effects, and resistance may occur. They also incompletely inhibit mTORC1 and have limited efficacy. Rapalink-1 is a bitopic inhibitor developed to overcome the limitations of rapalogs by linking rapamycin to a second-generation mTOR ATP competitive inhibitor, MLN0128. Here we explored the effect of Rapalink-1 on a TSC hamartoma model. The model is created by neonatal electroporation of mice having conditional Tsc2 genes. Prolonged Rapalink-1 treatment could be achieved with 1.5 or 3.0 mg/Kg injected intraperitoneally every five days. Rapalink-1 inhibited the mTORC1 pathway, decreased cell size, reduced neuron dendrite arbors, and reduced hamartoma size. In conclusion, these results demonstrate that cellular phenotypes in a TSC SEGA model are reversed by Rapalink-1 which may be useful to resolve TSC brain hamartomas.

neuroscience↗

bioRxiv2024

Molecular basis for plasma membrane recruitment of PI4KA by EFR3

The lipid kinase phosphatidylinositol 4 kinase III alpha (PI4KIII/PI4KA) is a master regulator of the lipid composition and asymmetry of the plasma membrane. PI4KA exists primarily in a heterotrimeric complex with its regulatory proteins TTC7 and FAM126. Fundamental to PI4KA activity is its targeted recruitment to the plasma membrane by the lipidated proteins EFR3A and EFR3B. Here, we report a cryo-EM structure of the C-terminus of EFR3A bound to the PI4KA-TTC7B-FAM126A complex, with extensive validation using both hydrogen deuterium exchange mass spectrometry (HDX-MS), and mutational analysis. The EFR3A C-terminus undergoes a disorder-order transition upon binding to the PI4KA complex, with an unexpected direct interaction with both TTC7B and FAM126A. Complex disrupting mutations in TTC7B, FAM126A, and EFR3 decrease PI4KA recruitment to the plasma membrane. Multiple post-translational modifications and disease linked mutations map to this site, providing insight into how PI4KA membrane recruitment can be regulated and disrupted in human disease. One sentence summaryThe cryo-EM structure of the C-terminus of EFR3A bound to the PI4KA complex reveals the molecular mechanism underlying PI4KA membrane localisation, and provides novel insight into PI4KA regulation and its involvement in human disease.

biochemistry↗