Biology subjects

Samantaray, K.

Publications and source records attributed to Samantaray, K..

3 recordsLinked to original sources

bioRxiv2026

Proteolytic control of mitochondrial calcium transport by intermembrane-space proteases

The mitochondrial intermembrane space (IMS) is a critical regulatory interface for mitochondrial calcium (mCa2+) flux. Positioned between the outer and inner mitochondrial membranes, the IMS links cytosolic Ca2+ signal to regulated Ca2+ uptake into the matrix. This positioning allows the IMS to influence mCa2+ transport and Ca2+-dependent mitochondrial metabolism. mCa2+ homeostasis is governed mainly by the mitochondrial calcium uniporter complex (mtCU), which mediates mCa2+ uptake, and the Na+/Ca2+ exchanger NCLX, which drives mCa2+ efflux. However, whether IMS regulatory events, particularly proteolytic remodeling by IMS proteases, control this transport machinery remains unclear. Using complementary knockout and overexpression approaches targeting ten IMS proteases (NLN, ATP23, IMMP1L, IMMP2L, YME1L1, OMA1, LACTB2, PARL, and HTRA2), we identified protease-specific remodeling of mtCU components and NCLX abundance. Transcriptomic and proteomic analyses showed that these changes arise largely from protease-specific control of transporter stability rather than transcriptional regulation alone. Proximity-labeling proteomics further revealed spatial associations between IMS proteases and mCa2+ transport components. Functionally, perturbing IMS proteases altered mCa2+ flux and reduced mCa2+ retention capacity, indicating impaired buffering against Ca2+ overload. Together, these findings identify IMS proteases as a proteostatic regulatory network controlling mCa2+ transport and establish a mechanistic link between mitochondrial proteostasis and Ca2+ homeostasis.

cell biology↗

bioRxiv2026

Lactylation landscape of mitochondrial proteins in myocardial infarction

Metabolic reprogramming is a hallmark of myocardial infarction (MI), in which cardiomyocytes shift from fatty acid oxidation to anaerobic glycolysis, leading to elevated lactate production and mitochondrial dysfunction. Lactylation, a recently described lysine post-translational modification, has emerged as a metabolic signaling mechanism; however, its role within mitochondria during MI remains poorly understood. Here, we define the mitochondrial lactylome following MI and examine how modulation of lactate transport influences mitochondrial metabolism and redox homeostasis. Using quantitative proteomics, we identify extensive remodeling of mitochondrial protein lactylation after MI, affecting enzymes involved in bioenergetics, redox regulation, and metabolic control. Pharmacological inhibition of monocarboxylate transporter-1 (MCT1) using AZD3965 further reshapes the mitochondrial lactylome, increasing lactylation of specific metabolic and redox-associated proteins without uniformly exacerbating mitochondrial dysfunction. Despite sustained impairment of global cardiac function, MCT1 inhibition attenuates post-MI fibrosis and inflammation and partially restores mitochondrial respiratory capacity. Consistent with in vivo findings, genetic or pharmacological inhibition of MCT1 in hypoxic cardiomyocytes-derived cells reduces mitochondrial reactive oxygen species, decreases inhibitory pyruvate dehydrogenase phosphorylation, and improves mitochondrial bioenergetics. Together, these findings reveal that mitochondrial lactylation is a context-dependent regulator of mitochondrial metabolism and redox balance following MI. Rather than acting solely as a pathological modification, lactylation integrates lactate availability with mitochondrial function to influence inflammatory and fibrotic remodeling, highlighting mitochondrial metabolic plasticity as a potential therapeutic target in ischemic heart disease. HighlightsO_LIMyocardial infarction (MI) increases mitochondrial protein lactylation, with 361 identified lactylated proteins. C_LIO_LIAZD3965-mediated MCT1 inhibition further elevates mitochondrial lactylation. C_LIO_LIDistinct alterations in mitochondrial proteins and pathways (TCA cycle, amino acid metabolism, gene expression) were observed. C_LIO_LIAZD3965 reduces cardiac fibrosis and inflammation and partly improves mitochondrial respiration post-MI, but cardiac function remains impaired. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/718938v1_ufig1.gif" ALT="Figure 1"> View larger version (47K): org.highwire.dtl.DTLVardef@b5a7b3org.highwire.dtl.DTLVardef@14ea92org.highwire.dtl.DTLVardef@1343a29org.highwire.dtl.DTLVardef@1d67716_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG

cell biology↗

bioRxiv2025

Peptidoglycan turnover promotes active transport of protein through the bacterial cell wall

The bacterial cell wall is a critical load-bearing structure, but is not thought to be an important permeability barrier since proteins freely diffuse through isolated cell wall sacculi and bacteria secrete proteins without the aid of any known channels or transporters in the wall. Using new genetically encoded probes to measure the permeability of the cell in situ at the single-cell level, we discovered that the size threshold determining whether proteins can pass through the Bacillus subtilis sacculus is smaller than was previously thought. We found that transport of small proteins (<10 kDa) through the sacculus was consistent with passive diffusion through discrete pores, while larger proteins (>15 kDa) required the generation of larger pores by inducing peptidoglycan hydrolysis unbalanced by synthesis. These data are consistent with physics-based models of diffusion through a random percolation network of finite thickness. Conversely, the ability of the innate immune factor phospholipase (15.2 kDa) to kill B. subtilis was inhibited by membrane de-polarization. The protective effect of de-polarization was dependent on latent peptidoglycan synthesis (decoupled from cell growth) by PBP1 - highlighting a new role for this enzyme - and on reduced peptidoglycan hydrolysis. These results demonstrate that the rapid peptidoglycan turnover that drives cell growth also promotes movement of phospholipase across the cell wall, identifying a quintessentially bacterial mechanism of active transport. Significance StatementGram-positive bacteria, which include many serious pathogens like Staphylococcus aureus, Listeria monocytogenes, and Clostridium difficile, are defined by their thick peptidoglycan cell wall. Here, we demonstrate that this structure is a critical permeability barrier that blocks antibacterial proteins like those used by the human innate immune system. Furthermore, this barrier function depends on the physiological state of the cell: the wall of non-growing cells is less permeable because peptidoglycan turnover during growth actively promotes transport of specific proteins through the cell wall. This prokaryotic paradigm for molecular transport has important implications for host-pathogen interactions since pathogenic bacteria often assume both non-growing and growing states during infection.

microbiology↗