Silbereis, J. | Search bioRxiv

bioRxiv2025

GPR17 structure and agonism with small molecules and oxysterols

GPR17 is a class A orphan GPCR that regulates myelination in the central nervous system. Inhibiting GPR17 is a potential therapeutic mechanism to induce remyelination. The limited understanding of the structural basis of GPR17 agonism and antagonism is a challenge for GPR17 drug discovery. We present novel cryo-EM structures of GPR17 with bound orthosteric antagonist or agonist/G protein heterotrimer with biophysical and cellular characterization to inform rational drug discovery. Both ligands bind towards a lateral edge of the orthosteric pocket, while an exceptionally long extracellular loop 2 occupies and limits access to this site. In contrast, pharmacological and photoaffinity studies indicate that endogenous oxysterol agonists of GPR17 bind allosterically. Characterization of oxysterol agonism versus a known orthosteric ligand in oligodendrocytes further supports an allosteric mechanism. Therefore, the design of more potent orthosteric ligands is limited by pocket size and accessibility. Targeting allosteric binding offers an alternative approach to GPR17 antagonism.

biochemistry↗

bioRxiv2024

Molecular Specification of Claustro-Amygdalar and Paleocortical Neurons and Connectivity

The ventropallial excitatory neurons (ExNs) in the claustro-amygdalar complex and piriform cortex (PIR; part of paleocortex) form crucial reciprocal connections with the prefrontal cortex (PFC), integrating cognitive and sensory information that result in adaptive behaviors. Early-life disruptions in these circuits are linked to neuropsychiatric disorders, highlighting the importance of understanding their development. Our study uncovers that transcription factors SOX4, SOX11, and TFAP2D play a pivotal role in the development, identity, and PFC connectivity of these neurons. Using mouse models, we demonstrate that the absence of transcription factors SOX4 and SOX11 in post-mitotic ExNs dramatically reduces the size of the basolateral amygdala complex (BLC), claustrum, and PIR. SOX4 and SOX11 control BLC formation through direct regulation of Tfap2d expression. Cross-species analyses, including humans, identified conserved Tfap2d expression in developing ExNs of BLC, claustrum, paleocortex including PIR, and the associated transitional areas of the frontal, insular and temporal cortex. While the loss and haploinsufficiency of Tfap2d yield similar alterations in learned threat behaviors, differences emerge in the manifestation of Tfap2d dosage, particularly in terms of changes observed in BLC size and the connectivity pattern between the BLC and PFC. This underscores the significance of Tfap2d dosage in orchestrating developmental shifts in BLC-PFC connectivity and behavioral modifications reminiscent of symptoms of neuropsychiatric disorders. Together, these findings reveal key elements of a conserved gene regulatory network that shapes the development and function of crucial ventropallial ExNs and their PFC connectivity and offer insights into their evolution and alterations in neuropsychiatric disorders.

neuroscience↗