Biology subjects

Sohn, J.-W.

Publications and source records attributed to Sohn, J.-W..

4 recordsLinked to original sources

bioRxiv2024

Adaptive thermogenesis is mediated by GDF15 via the GFRAL neuronal axis in mice

Adaptive thermogenesis is a key homeostatic mechanism that primarily occurs in brown adipocytes and enables the maintenance of body temperature. Although this process involves coordinated responses in multiple tissues, including the browning of white adipocytes, the precise inter-organ crosstalk underlying adaptive thermogenesis is unclear. Here, we investigate the pivotal role of the GDNF family receptor alpha-like (GFRAL) neuronal axis in modulating compensatory thermogenic responses in brown and white adipose depots under stress conditions, specifically the mitochondrial unfolded protein response resulting from genetic modification and cold exposure. We employed a mouse model with targeted deletion of Crif1 in the mitoribosomes of brown adipocytes, and cold-exposed mice and immortalized adipocytes, to uncover the mechanism by which mitochondrial stress-induced growth differentiation factor 15 (GDF15) expression affects metabolism and facilitates adaptive thermogenesis. We found that Crif1 deletion resulted in browning of inguinal white adipose depots, increased energy expenditure, reduced food intake, and resistance to weight gain. Retrograde neuronal tracing established that GFRAL-positive neurons in the hindbrain and sympathetic preganglionic neurons in the spinal cord mediated the GDF15-associated browning of inguinal white adipose tissue. Intervention studies using antisense oligonucleotides to inhibit Gfral expression blunted the effect of Crif1 deletion on energy expenditure and food intake, further confirming the essential role the GFRAL axis plays in GDF15-driven thermogenic adaptation in white adipose tissue. Our findings suggest that the GFRAL neuronal axis is key in coordinating the adaptive thermogenic response across multiple tissues and adipose depots, thereby ensuring metabolic homeostasis during mitochondrial stress.

molecular biology↗

bioRxiv2023

A Normative Framework Dissociates Need and Motivation in Hypothalamic Neurons

Physiological needs evoke motivational drives to produce natural behaviours for survival. However, the temporally intertwined dynamics of need and motivation have made it challenging to differentiate these two components in previous experimental paradigms. Based on classic homeostatic theories, we established a normative framework to derive computational models of neural activity and behaviours for need-encoding and motivation-encoding neurons during events that induce predicted gain or loss. We further developed simple and intuitive experimental paradigms that enabled us to distinguish the distinct roles of subpopulations of neurons in the hypothalamus. Our results show that AgRP neurons and LHLepR neurons are consistent with need and motivation, respectively. Our study provides a parsimonious understanding of how distinct hypothalamic neurons separately encode need and motivation to produce adaptive behaviours for maintaining homeostasis.

neuroscience↗

bioRxiv2021

Gabra5LHA Mediate Astrocytic GABA-induced Obesity via Decreasing Energy Expenditure

The lateral hypothalamic area (LHA) regulates food intake and energy expenditure. Although LHA neurons innervate adipose tissues, the identity of neurons that regulate fat is undefined. Here we identify that Gabra5-positive neurons in LHA (GABRA5LHA) polysynaptically project to brown and white adipose tissues in the periphery. GABRA5LHA are a distinct subpopulation of GABAergic neurons and show decreased pacemaker firing in diet-induced obesity (DIO) mouse model. Chemogenetic inhibition of GABRA5LHA suppresses energy expenditure and increases weight gain, whereas gene-silencing of Gabra5 in LHA decreases weight gain. In DIO mouse model, GABRA5LHA are tonically inhibited by nearby reactive astrocytes releasing GABA, which is synthesized by MAOB. Gene-silencing of astrocytic MAOB in LHA reduces weight gain significantly without affecting food intake, which is recapitulated by administration of a MAOB inhibitor, KDS2010. We propose that firing of GABRA5LHA facilitates energy expenditure and selective inhibition of astrocytic GABA is a molecular target for treating obesity.

neuroscience↗

bioRxiv2021

Lomitapide, a cholesterol-lowering drug, is an anticancer agent that induces autophagic cell death via inhibiting mTOR

Autophagy is a biological process that maintains cellular homeostasis and regulates the internal cellular environment. Hyperactivating autophagy to trigger cell death has been a suggested therapeutic strategy for cancer treatment. Mechanistic target of rapamycin (mTOR) is a crucial protein kinase that regulates autophagy; therefore, using a structure-based virtual screen analysis, we identified lomitapide, a cholesterol-lowering drug, as a potential mTOR complex 1 (mTORC1) inhibitor. Our results showed that lomitapide directly inhibits mTORC1 in vitro and induces autophagy-dependent cancer cell death by decreasing mTOR signaling, thereby inhibiting the downstream events associated with increased LC3 conversion in various cancer cells (e.g., HCT116 colorectal cancer cells) and tumor xenografts. Lomitapide also significantly suppresses the growth and viability along with elevated autophagy in patient-derived colorectal cancer organoids. Furthermore, a combination of lomitapide and immune checkpoint blocking antibodies synergistically inhibits tumor growth in murine MC-38 or B16-F10 pre-clinical syngeneic tumor models. These results elucidates the direct, tumor-relevant immune-potentiating benefits of mTORC1 inhibition by lomitapide, which complement the current immune checkpoint blockade. This study highlights the potential repurposing of lomitapide as a new therapeutic option for cancer treatment.

cancer biology↗