Biology subjects

Waingankar, T. P.

Publications and source records attributed to Waingankar, T. P..

4 recordsLinked to original sources

bioRxiv2026

Uncovering moonlighting role of mitochondrial presequence translocase machinery in SOD1-mediated ALS pathogenesis

Familial Amyotrophic Lateral Sclerosis (fALS) is a fatal neurodegenerative disease, mainly caused by mutations in the superoxide dismutase 1 (SOD1) protein. Mitochondrial dysfunction is a primary hallmark of ALS pathogenesis. However, the molecular mechanism by which SOD1 mutants impair organellar health remains enigmatic. This study demonstrates that mutant SOD1 associates with the TIM23 complex in Saccharomyces cerevisiae via its intermembrane space (IMS) domain. In ALS-associated SOD1 mutants, both binding and expression of TIM23 complex proteins were downregulated, leading to altered translocation of the substrate protein Sdh3, a component of the electron transport chain (ETC) complex II. Disrupted Sdh3 translocation leads to mitochondrial dysfunction, evidenced by decreased ETC complex II activity, reduced functional mass, and compromised organelle integrity. Overexpression of Tim23 partially rescued mitochondrial integrity by increasing ETC complex activity and functional mass and restoring reticular morphology. Strikingly, the improved mitochondrial homeostasis in Tim23-overexpressing cells partially rescued the growth defects caused by mutant SOD1. Collectively, these findings reveal a previously unrecognized regulatory axis between mutant SOD1 and the mitochondrial pre-sequence translocase machinery, highlighting this pathway as a promising target for future ALS therapies and opening new avenues for mechanistic and translational research. Author SummaryFamilial Amyotrophic Lateral Sclerosis (fALS) is a progressive, fatal neuromuscular disorder marked by motor neuron degeneration. The exact cause of ALS remains unclear. Previous research links familial ALS to mutations in the superoxide dismutase 1 (SOD1) gene. SOD1 mutants in ALS disrupt mitochondrial protein translocation, a key mitochondrial process. The mechanism by which SOD1 mutants affect mitochondrial function and integrity by modulating presequence translocase (TIM23 complex) import is not yet understood. The current study addresses a critical gap in ALS research by demonstrating a novel, direct interaction between SOD1 and Tim23 that regulates mitochondrial function in yeast. We found that SOD1 binds Tim23 via Tim23 IMS domain, stabilizes the Tim23CORE complex, enabling Sdh3 import. Loss of SOD1, Tim23, or Tim50 destabilizes the TIM23CORE complex, leading to impaired Sdh3 import and decreased ETC complex-II activity. These changes disrupt mitochondrial structure, causing fragmentation and a loss of functional mitochondrial mass in {Delta}sod1. ALS-linked SOD1 mutants show similar effects: they diminish Sdh3 import by weakening SOD1-Tim23 interaction and lowering TIM23 complex stability, resulting in punctate mitochondria and reduced mitochondrial mass. Collectively, our study identifies the SOD1-TIM23 interaction as a key regulator of mitochondrial health through Sdh3 import via the TIM23CORE complex and indicates this pathway as a potential early intervention target for ALS therapy.

genetics↗

bioRxiv2025

Self-renewal of neuronal mitochondria through asymmetric division

Mitochondrial ATP production is essential for life. Mitochondrial function depends on the spatio-temporal coordination of nuclear and mitochondrial genome expression, yet how this coordination occurs in highly polarized cells such as neurons remains poorly understood. Using high-resolution imaging in mouse peripheral sensory neurons and zebrafish larvae, we identified a sub-population of mitochondria enriched in mtDNA that are positioned at the collateral branch points of long sensory neurites, both in vitro and in vivo. While the mitochondria in neurites are generally depleted of mtDNA, those at axon branch points preferentially engage in mtDNA replication and transcription, accumulate nuclear-encoded mitochondrial mRNA, and are spatially linked to nascent cytosolic peptide synthesis. The mtDNA-positive mitochondrial pool exhibits asymmetric genome partitioning at division, shedding highly motile daughters that lack mtDNA. Asymmetric division rejuvenates the membrane potential of the mtDNA-rich, biogenesis-dedicated mitochondria. We also found that, in peripheral sensory neurons, axonal mitochondria rarely fuse or share matrix contents, explaining how differentiated daughters maintain their distinct composition and fate after fission. Thus, division-coupled mitochondrial self-renewal is yoked to neurite topology in sensory neurons, patterning mitochondrial diversity and homeostasis from micron to meter scales.

cell biology↗

bioRxiv2025

Saturated lipid stress attenuates mitochondrial genome synthesis in human cells

Fatty acids are trafficked between organelles to support membrane biogenesis and act as signaling molecules to rewire cellular metabolism in response to starvation, overnutrition, and environmental cues. Mitochondria are key cellular energy converters that harbor their own multi-copy genome critical to metabolic control. In homeostasis, mitochondrial DNA (mtDNA) synthesis is coupled to mitochondrial membrane expansion and division at sites of contact with the endoplasmic reticulum (ER). Here, we provide evidence from cultured hepatocytes that mtDNA synthesis and lipid droplet biogenesis occur at spatially and functionally distinct ER-mitochondria membrane contact sites. We find that, during saturated lipid stress, cells pause mtDNA synthesis and mitochondrial network expansion secondary to rerouted fatty acid trafficking through the ER and lipid droplet biogenesis, coincident with a defect in soluble protein import to the ER lumen. The relative composition of fatty acid pools available to cells is critical, as monounsaturated fatty acid supplementation rescued both ER proteostasis and mtDNA synthesis, even in the presence of excess saturated fat. We propose that shutoff of mtDNA synthesis conserves mtDNA-to-mitochondrial network scaling until cells can regain ER homeostasis. SummaryOvernutrition of cultured human cells causes endoplasmic reticulum dysfunction, which downregulates mitobiogenesis in turn by constraining mtDNA synthesis.

cell biology↗

bioRxiv2024

A spatial atlas of mitochondrial gene expression reveals dynamic translation hubs and remodeling in stress

Mitochondrial genome expression is important for cellular bioenergetics. How mitochondrial RNA processing and translation are spatially organized across dynamic mitochondrial networks is not well understood. Here, we report that processed mitochondrial RNAs are consolidated with mitoribosome components into translation hubs distal to either nucleoids or processing granules in human cells. During stress, these hubs are remodeled into translationally repressed mesoscale bodies containing messenger, ribosomal, and double-stranded RNA. We show that the highly conserved helicase SUV3 contributes to the distribution of processed RNA within mitochondrial networks, and that stress bodies form downstream of proteostatic stress in cells lacking SUV3 unwinding activity. We propose that the spatial organization of nascent chain synthesis into discrete domains serves to throttle the flow of genetic information in stress to ensure mitochondrial quality control.

cell biology↗