Biology subjects

Siddiqui, T.

Publications and source records attributed to Siddiqui, T..

3 recordsLinked to original sources

bioRxiv2025

Altered lysosomal biology impairs motor neuron survival via TFEB dysregulation in spinal muscular atrophy

Spinal muscular atrophy (SMA) is a devastating motor neuron disease, caused by recessive mutations or deletions of the SMN1 gene, representing the leading genetic cause of infant mortality. Available therapies, aimed at increasing SMN protein levels, can only partially halt motor neuron (MN) degeneration in a select number of patients, reinforcing the need for combinatorial treatments to improve clinical outcomes. We previously showed that mTORC1 overactivation and impaired autophagosome clearance in SMA MNs lead to the accumulation of protein aggregates, contributing to MN degeneration. However, the mechanistic link between SMN protein deficiency and autophagy-lysosomal dysfunction remained unknown. Here, using patient iPSC-derived MNs along with isogenic and healthy controls, we show that SMA MNs exhibit reduced lysosome numbers and impaired functionality. Furthermore, the master regulator of lysosomal biogenesis and autophagy, TFEB, is downregulated, and its nuclear translocation compromised upon SMN deficiency. We further propose the upregulation of the mTORC1 positive modulator TPT1 as contributor to TFEB dysregulation. Notably, TFEB overexpression ameliorates protein aggregate accumulation in SMA MNs and enhances MN survival both in vitro and in a zebrafish SMA model. Our findings identify lysosomal dysfunction as a key player in SMA pathology and highlight TFEB activation as a potential therapeutic strategy for SMA treatment. One Sentence SummaryTFEB activation restores lysosomal function and improves motor neuron survival in SMA, highlighting its potential as a therapeutic target.

neuroscience↗

bioRxiv2024

Identification of Thioredoxin1 interacting proteins in neuronal cytoskeletal organization during autophagy

Thioredoxin1 (Trx1) is a major cytoplasmic thiol oxidoreductase protein involved in redox signaling. This function is rendered by a rapid electron transfer reaction during which Trx1 reduces its substrate and itself becomes oxidized. In this reaction, Trx1 forms a transient disulfide bond with the substrate which is unstable and therefore identification of Trx1 substrates is technically challenging. This process maintains the cellular proteins in a balanced redox state and ensures cellular homeostasis. Trx1 levels are reduced in some neurodegenerative diseases; therefore, understanding the interactions between Trx1 and its substrates in neurons could have significant therapeutic implications. We utilized a transgenic mouse model expressing a Flag-tagged mutant form of Trx1 that can form stable disulfide bonds with its substrates allowing identification of the Trx1 interacting proteins. The involvement of Trx1 has been suggested in autophagy, we aimed to investigate Trx1 substrate after pharmacologic induction of autophagy in primary hippocampal neurons. Treatment of primary neurons by rapamycin, a standard autophagy inducer, caused significant reduction of neurite outgrowth and alterations in the cytoskeleton. Through immunoprecipitation and mass spectrometry, we have identified 77 Trx1 interacting proteins which were associated with a wide range of cellular functions including a major impact on cytoskeletal organization. The results were confirmed in Trx1 knocked-down cells and in nucleofected primary neurons. Our study suggests a novel role for Trx1 in regulation of neuronal cytoskeleton organization, marking the first investigation of Trx1-interacting proteins in primary neurons and confirming the multifaceted role of Trx1 in physiological and pathological states.

biochemistry↗

bioRxiv2022

Neurogenic induction by Ngfr reduces reactive astrocytic Lcn2/Slc22a17 signalling, amyloid deposition and Tau phosphorylation

Neurogenesis relates to the brain resilience and is reduced in Alzheimers disease (AD). Restoring healthy levels of neurogenesis could have beneficial effects for coping with neurodegeneration. However, molecular mechanisms that could enhance neurogenesis from astroglial progenitors in AD pathology are largely unknown. We used lentiviruses to express Ngfr in the hippocampus of the APP/PS1dE9 mouse model of AD, histologically analyzed the changes in proliferation of neural stem cells and neurogenesis; performed single-cell transcriptomics, spatial proteomics, and functional knockdown studies. We found that expression of Ngfr, a neurogenic determinant in pathology-induced neuroregeneration in zebrafish, stimulated proliferative and neurogenic outcome in the APP/PS1dE9 AD mouse model. Ngfr suppressed reactive astrocyte marker Lipocalin-2 (Lcn2) in astroglia. Blockage of Lcn2 receptor, Slc22a17, recapitulated the neurogenic effects of NGFR, and long-term Ngfr expression reduced amyloid plaques and Tau phosphorylation. Furthermore, immunostaining on postmortem human hippocampi with AD or primary age-related Tauopathy and 3D human astroglial cultures showed that elevated LCN2 levels correlate with gliosis. By comparing transcriptional changes in mouse hippocampus, zebrafish brain, and human AD brains in terms of cell intrinsic differential gene expression analyses as well as weighted gene co-expression network analysis, we observed common potential downstream effectors of NGFR signaling, C4B and PFKP, that are relevant to AD. Our study links the regulatory role of an autocrine molecular mechanism in astroglia to the neurogenic ability and modulatory effects on amyloid and tau phosphorylation, opening new research avenues and suggesting that neurogenesis-oriented therapeutic approaches could be a potential clinical intervention for AD.

neuroscience↗