Prina, M. L. | Search bioRxiv

bioRxiv2026

Scaling of Neuronal Growth and Excitability Through Separable mTORC1 and mTORC2 Pathways

As neurons grow, they must regulate intrinsic excitability to maintain an appropriate level of spiking based on synaptic inputs. Using gene knockouts, phosphoproteomics, and electrophysiology we show PTEN regulates neuronal growth and intrinsic excitability through separable downstream mechanisms. Pten loss induces cellular hypertrophy, increased excitatory synaptic input, reduced fast afterhyperpolarization, and burst firing. Deleting the mTORC1 scaffold, Raptor, rescues overgrowth and synaptic input but fails to normalize firing, while deleting Akt or the mTORC2 scaffold, Rictor, restores firing without rescuing growth. This dissociation identifies an AKT-mTORC2 mechanism that regulates voltage-gated calcium and BK potassium channels to set spike repolarization and burst firing. In vivo, Pten knockout produces altered network synchrony, lethal seizures, and impaired object and location behavior; Raptor co-deletion display non-lethal hyperexcitability with improved object-location coupling. The biological and pathophysiological significance of these mechanisms is demonstrated by overlap of the PTEN-regulated phosphoproteome with ASD and epilepsy.

neuroscience↗

bioRxiv2026

PTEN Subcellular Localization Dictates Function

Mutations in phosphatase and tensin homolog (PTEN) drive unregulated activation of the phosphatidylinositol-3-kinase (PI3K) pathway, resulting in neuronal hypertrophy, and are strongly associated with autism spectrum disorder (ASD). Several PTEN mutations alter subcellular localization, yet how localization governs PTEN function in developing neurons remains unclear. Although PTEN has been reported broadly distributed throughout neurons, here, live imaging of HaloTagged PTEN reveals dynamically regulated localization, suggesting spatial control of its signaling. We then used retroviral-mediated genetic manipulation to delete endogenous Pten in developing hippocampal neurons while simultaneously expressing PTEN fused to defined localization motifs, allowing us to directly test how subcellular targeting regulates neuronal morphology. Loss of Pten produces neurons characterized by enlarged somata, more elaborate dendritic arbors, and increased spine density, length, and head area. Nuclear-excluded PTEN fully rescued these phenotypes, whereas targeting PTEN to filopodia via fusion to the FBAR domain of srGAP3 or to the postsynaptic density via Homer1C corrected or corrected all morphological abnormalities in PTEN-deficient neurons and simplified dendritic arborization compared to wild-type. In contrast, nuclear-localized PTEN produced only partial rescue, normalizing soma size and spine head area but not dendritic complexity or spine density. These findings indicate that PTEN acts locally to restrain growth and structural connectivity, whereas regulation of spine head size can be mediated by PTEN both inside and outside the nucleus, potentially through transcriptional or splicing-dependent mechanisms. Together, our results identify subcellular localization as a critical determinant of PTEN function and reveal spatially distinct mechanisms through which PTEN sculpts neuronal development.

neuroscience↗