Biology subjects

Pulinilkunnil, T.

Publications and source records attributed to Pulinilkunnil, T..

4 recordsLinked to original sources

bioRxiv2025

beta3-adrenergic browning of pericardial adipose tissue controls cardiac function

Dysfunctional adipose tissue (AT) is strongly linked to the development of cardiovascular diseases (CVD). Accumulation of AT around vital organs is detrimental to their respective function and overall health. Although there is strong evidence linking the accumulation of pericardial AT with CVD development, a comprehensive investigation on the adaptation of pAT in obesity is scarce. Here, by applying pair-wise bottom-up proteomics in pAT of humans and mice, we found pAT presents a browning signature, as demonstrated by enrichment of mitochondria, presence of UCP1, and greater metabolic capacity compared to subcutaneous AT. In mice fed a high-fat diet or obese patients, the pAT undergoes whitening, characterized by adipocyte hypertrophy, reduced mitochondrial content, respiratory capacity, and UCP1 levels. Lipectomy of pAT from obese mice decreased pathological ventricular hypertrophy. Conversely, selective {beta}3-adrenergic agonist treatment rescued pAT browning status and is associated with improved heart structure and function, including ventricular thickness, and fibrosis in obese mice. Importantly, lipectomy of pAT abrogated the positive effects of {beta}3-adrenergic agonism in cardiac function of obese mice. Altogether, our work positions pAT as a mechanistic driver of obesity-related cardiac dysfunction and establish {beta}3-adrenergic-mediated browning of pAT as a novel therapeutic treatment strategy.

physiology↗

bioRxiv2025

TRPML1 signaling at lysosomes-mitochondria nexus drives triple-negative breast cancer mitophagy, metabolic reprogramming and chemoresistance

Inter-organelle signaling mechanisms, particularly those at the lysosomes-mitochondria interface, are critical for cancer cell metabolism, mitophagy and survival. However, the incomplete understanding of these mechanisms has limited the development of effective therapies, especially for triple-negative breast cancers (TNBC). Here, we demonstrate the lysosomal Ca{superscript 2}-release channel TRPML1 as a master regulator of mitochondrial bioenergetics in TNBC cells. TRPML1 knockdown (ML1-KD) in TNBC cells selectively compromises mitochondrial respiration, reprograms cell metabolism, and induces mitochondrial fragmentation without impacting non-cancerous cells. Mitochondria of ML1-KD TNBC cells sequester around the endoplasmic reticulum (ER), increasing mitochondria-ER contact sites at the expense of mitochondria-lysosomes contacts. Mechanistically, ML1-KD reduces lysosomal acidification, thus hindering autophagic flux and completion of autophagy. ML1-KD inhibits TFEB-mediated mitophagy and oxidative defense mechanisms while causing mitochondrial Ca2+ overload, further impairing mitochondrial function. These alterations render ML1-KD TNBC cells highly sensitive to doxorubicin and paclitaxel at low doses that are typically ineffective on their own. Together, our findings establish TRPML1 as a critical inter-organelle regulator and highlight its potential as a therapeutic target to exploit the metabolic vulnerabilities of TNBC cells.

cancer biology↗

bioRxiv2021

Inhibiting BCKDK in triple-negative breast cancer suppress protein translation, impair mitochondrial function, and potentiate doxorubicin cytotoxicity

Triple-negative breast cancers (TNBCs) are characterized by poor survival, prognosis and gradual resistance to cytotoxic chemotherapeutics, like doxorubicin (DOX), which is limited by its cardiotoxic and chemoresistant effects that manifest over time. TNBC growth and survival are fuelled by reprogramming branched-chain amino acids (BCAAs) metabolism, which rewires oncogenic gene expression and cell signaling pathways. A regulatory kinase of the rate-limiting enzyme of the BCAA catabolic pathway, branched-chain ketoacid dehydrogenase kinase (BCKDK), have recently been implicated in driving tumor cell proliferation and conferring drug resistance by activating RAS/RAF/MEK/ERK signaling. However it remains unexplored if BCKDK remodels TNBC proliferation, survival and susceptibility to DOX-induced genotoxic stress. TNBC cell lines exhibited reduced BCKDK expression in response to DOX. Genetic and pharmacological inhibition of BCKDK in TNBC cell lines displayed reduced intracellular and secreted BCKAs. Moreover, BCKDK inhibition with concurrent DOX treatment exacerbated apoptosis, caspase activity and loss of TNBC proliferation. Transcriptome analysis of BCKDK silenced cells confirmed a marked upregulation of the apoptotic signaling pathway with increased protein ubiquitylation and compromised mitochondrial metabolism. BCKDK silencing in TNBC downregulated mitochondrial metabolism genes, reduced electron complex protein expression, oxygen consumption and ATP production. Silencing BCKDK in TNBC upregulated sestrin 2 and concurrently decreased protein synthesis and mTORC1 signaling. Inhibiting BCKDK in TNBC remodel BCAA flux, reduces protein translation triggering cell death, ATP insufficiency and susceptibility to genotoxic stress. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=137 SRC="FIGDIR/small/444634v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@19d375eorg.highwire.dtl.DTLVardef@9dfe2corg.highwire.dtl.DTLVardef@9a1eecorg.highwire.dtl.DTLVardef@642fdb_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2020

Silencing branched-chain ketoacid dehydrogenase or treatment with branched-chain ketoacids ex vivo inhibits muscle insulin signaling

Branched-chain -keto acids (BCKAs) are downstream catabolites of branched-chain amino acids (BCAAs). Mitochondrial oxidation of BCKAs is catalyzed by branched-chain ketoacid dehydrogenase (BCKDH), an enzyme sensitive to inhibitory phosphorylation by BCKD kinase (BCKDK). Emerging studies show that defective BCAA catabolism and elevated BCKAs levels correlate with glucose intolerance and cardiac dysfunction. However, if/how BCKDH and BCKDK exert control on the availability and flux of intramyocellular BCKAs and if BCKA reprograms nutrient metabolism by influencing insulin action remains unexplored. We observed altered BCAA catabolizing enzyme expression in the murine heart and skeletal muscle during physiological fasting and diet-induced obesity and after ex vivo exposure of C2C12 cells to increasing concentration of saturated fatty acid, palmitate. BCKAs per se impaired insulin-induced AKT phosphorylation and AKT activity in skeletal myotubes and cardiomyocytes. In skeletal muscle cells, mTORC1 and protein translation signaling was enhanced by BCKA with concomitant suppression of mitochondrial respiration. Lowering intracellular BCKA levels by genetic and pharmacological activation of BCKDHA enhanced insulin signaling and activated pyruvate dehydrogenase, an effector of glucose oxidation and substrate metabolism. Our findings suggest that BCKAs profoundly influence muscle insulin function, providing new insight into the molecular nexus of BCAA metabolism and signaling with cellular insulin action and respiration.

cell biology↗