bioRxiv Science⌕ Search

Biology subjects

Karra, T.

Publications and source records attributed to Karra, T..

2 recordsLinked to original sources

Tau interactions with inner nuclear envelope proteins modulates chromatin

Abstract/SummaryThe intracellular re-distribution of the neuronal microtubule-associated protein Tau, from the axon into the somatodendritic compartment, is a physiological stress-related event and occurs early in Alzheimers disease (AD). Nuclear envelope distortions have been linked to the presence and aggregation of pathological Tau near the nucleus in these diseases. How physiologically increased soma Tau levels, enabling Tau interactions with the nucleus, impact nuclear integrity and neuronal physiology is unclear. Combining proximity biotinylation interactomics with chromatin imaging and molecular assays, we show that soluble Tau interacts with proteins coordinating chromatin at the inner nuclear membrane, including lamin B receptor and SUN1. This interaction promotes nuclear envelope invaginations and damage and changes the coordination of DNA at the nuclear lamina. Increasing somatodendritic Tau is sufficient to upregulate the expression of multiple transcription factors implicated in AD pathogenesis and to reduce expression of genes involved in cholesterol biosynthesis, which seem coordinated at lamin associated domains. These nuclear envelope-related mechanisms suggest that physiological, neuronal stress-related somatodendritic Tau missorting can initiate chromatin-related cascades important for early changes in AD and tauopathies.

neuroscience↗

Insulin resistance alters cortical inhibitory neurons and microglia to exacerbate Alzheimer knock-in mouse phenotypes

Metabolic dysfunction contributes to the risk and progression of Alzheimer"s disease (AD) through insulin signaling, but the cellular mechanisms are not fully understood. In this study, we examined the effects of streptozotocin-induced insulin deficiency or a high-fat, high-sugar (HFHS) diet-induced insulin resistance on cognitive function in knock-in AD mouse models expressing human mutant APP and wild-type tau. Both metabolic perturbations caused hyperglycemia, but only the HFHS diet resulted in weight gain and greater learning and memory deficits. The HFHS diet exacerbation occurred without changes in amyloid-{beta} or phospho-tau accumulation and with only subtle alterations in microglial morphology. The basis for functional deficits was explored with single-nucleus transcriptomic analysis. Prominent gene expression changes in glial cells and cerebral cortex Layer 2 inhibitory neurons correlated with the enhanced behavioral deficits. In HFHS-fed AD mice, we observed a shared metabolic impairment in neurodegeneration (MinD) state across multiple glial cell types. Additionally, the HFHS diet, with or without AD pathology, induced selective upregulation of the transcription factor Meis2 in cortical Layer 2 inhibitory neurons, in association with pathways involved in cell excitability. Overall, these findings suggest that HFHS-driven metabolic stress affects brain function and behavior through specific cellular programs distinct from amyloid or tau pathology, and identifies new targets that link diet-induced metabolic stress to cognitive decline in AD.

neuroscience↗