STIM1 functions as a proton sensor to coordinate cytosolic pH with store-operated calcium entry.

The meticulous regulation of intracellular pH (pH) is crucial for maintaining cellular function and homeostasis, impacting physiological processes such as heart rhythm, cell migration, proliferation, and differentiation. Dysregulation of pH is implicated in various pathologies such as arrhythmias, cancer, and neurodegenerative diseases. Here, we explore the role of STIM1, an ER calcium (Ca) sensor mediating Store Operated Ca Entry (SOCE), in sensing pH changes.

Role of STIM1 in the Regulation of Cardiac Energy Substrate Preference.

The heart requires a variety of energy substrates to maintain proper contractile function. Glucose and long-chain fatty acids (FA) are the major cardiac metabolic substrates under physiological conditions. Upon stress, a shift of cardiac substrate preference toward either glucose or FA is associated with cardiac diseases.

Ketone Body Exposure of Cardiomyocytes Impairs Insulin Sensitivity and Contractile Function through Vacuolar-Type H-ATPase Disassembly-Rescue by Specific Amino Acid Supplementation.

The heart is metabolically flexible. Under physiological conditions, it mainly uses lipids and glucose as energy substrates. In uncontrolled diabetes, the heart switches towards predominant lipid utilization, which over time is detrimental to cardiac function.

Specific amino acid supplementation rescues the heart from lipid overload-induced insulin resistance and contractile dysfunction by targeting the endosomal mTOR-v-ATPase axis.

Objective: The diabetic heart is characterized by extensive lipid accumulation which often leads to cardiac contractile dysfunction. The underlying mechanism involves a pivotal role for vacuolar-type H-ATPase (v-ATPase, functioning as endosomal/lysosomal proton pump). Specifically, lipid oversupply to the heart causes disassembly of v-ATPase and endosomal deacidification.

Augmenting Vacuolar H-ATPase Function Prevents Cardiomyocytes from Lipid-Overload Induced Dysfunction.

The diabetic heart is characterized by a shift in substrate utilization from glucose to lipids, which may ultimately lead to contractile dysfunction. This substrate shift is facilitated by increased translocation of lipid transporter CD36 (SR-B2) from endosomes to the sarcolemma resulting in increased lipid uptake. We previously showed that endosomal retention of CD36 is dependent on the proper functioning of vacuolar H-ATPase (v-ATPase).

Microbial-Driven Butyrate Regulates Jejunal Homeostasis in Piglets During the Weaning Stage.

Microbe-derived butyrate plays an important role in the gut health of young mammals during the weaning stage. A greater understanding of how butyrate regulates intestinal development is necessary for overcoming post-weaning diarrheal diseases. We aimed to investigate whether jejunal microbial metabolite butyrate modulates the apoptosis/proliferation balance and immune response in piglets during the post-weaning period of the first 3 weeks of life.

A new set of reference housekeeping genes for the normalization RT-qPCR data from the intestine of piglets during weaning.

The intestinal mucosal development of piglets (Sus scrofa) during the weaning stage is important to their disease susceptibility and later growth. Quantitative real-time PCR (RT-qPCR) is commonly used to screen for differentially expressed genes and, for accurate results, proper reference housekeeping genes are essential. Here we assessed the mRNA expression of 18 well-known candidate reference genes at different parts of the gastrointestinal tract (GIT) of piglets during the weaning process by RT-qPCR assay.

Acute and Chronic Effects of Protein Kinase-D Signaling on Cardiac Energy Metabolism.

Protein kinase-D (PKD) is increasingly recognized as a key regulatory signaling hub in cardiac glucose uptake and also a major player in the development of hypertrophy. Glucose is one of the predominant energy substrates for the heart to support contraction. However, a cardiac substrate switch toward glucose over-usage is associated with the development of cardiac hypertrophy.

Molecular mechanisms underlying inhibition of STIM1-Orai1-mediated Ca entry induced by 2-aminoethoxydiphenyl borate.

Store-operated Ca entry (SOCE) mediated by STIM1 and Orai1 is crucial for Ca signaling and homeostasis in most cell types. 2-Aminoethoxydiphenyl borate (2-APB) is a well-described SOCE inhibitor, but its mechanisms of action remain largely elusive. Here, we show that 2-APB does not affect the dimeric state of STIM1, but enhances the intramolecular coupling between the coiled-coil 1 (CC1) and STIM-Orai-activating region (SOAR) of STIM1, with subsequent reduction in the formation of STIM1 puncta in the absence of Orai1 overexpression.

Proteomic mapping of ER-PM junctions identifies STIMATE as a regulator of Ca²⁺ influx.

Specialized junctional sites that connect the plasma membrane (PM) and endoplasmic reticulum (ER) play critical roles in controlling lipid metabolism and Ca(2+) signalling. Store-operated Ca(2+) entry mediated by dynamic STIM1-ORAI1 coupling represents a classical molecular event occurring at ER-PM junctions, but the protein composition and how previously unrecognized protein regulators facilitate this process remain ill-defined. Using a combination of spatially restricted biotin labelling in situ coupled with mass spectrometry and a secondary screen based on bimolecular fluorescence complementation, we mapped the proteome of intact ER-PM junctions in living cells without disrupting their architectural integrity.

Inside-out Ca(2+) signalling prompted by STIM1 conformational switch.

Store-operated Ca(2+) entry mediated by STIM1 and ORAI1 constitutes one of the major Ca(2+) entry routes in mammalian cells. The molecular choreography of STIM1-ORAI1 coupling is initiated by endoplasmic reticulum (ER) Ca(2+) store depletion with subsequent oligomerization of the STIM1 ER-luminal domain, followed by its redistribution towards the plasma membrane to gate ORAI1 channels. The mechanistic underpinnings of this inside-out Ca(2+) signalling were largely undefined.