Paola de Los Heros

Cardiomyopathies are a major category of cardiovascular disease, significantly contributing to global morbidity and mortality. Their pathogenesis involves a complex interplay of genetic and environmental factors, with multiple gene families playing critical roles in disease progression. Among these, the Solute Carrier 12A (SLC12A) family encodes membrane cation-coupled chloride cotransporters (CCCs), which are essential for ion transport and cellular homeostasis. By regulating intracellular chloride and potassium concentrations, SLC12A/CCC transporters may directly influence myocardial electrophysiology, repolarization dynamics, and susceptibility to cardiomyopathies. Dysfunction of potassium-handling cotransporters can disrupt action potential propagation, increasing the risk of arrhythmias, while chloride transport abnormalities exacerbate ischemic injury by impairing cell volume regulation and metabolic responses to hypoxia. This review examines the expression and protein levels of SLC12A/CCCs in cardiac tissue, providing crucial insights into their functional significance for maintaining cardiac ion homeostasis. Understanding the regulatory mechanisms of these transporters could inform therapeutic interventions to restore ion balance and mitigate myocardial dysfunction in affected patients, thereby improving cardiac health.

Cardiomyopathies are a major category of cardiovascular disease, significantly contributing to global morbidity and mortality. Their pathogenesis involves a complex interplay of genetic and environmental factors, with multiple gene families playing critical roles in disease progression. Among these, the Solute Carrier 12A (SLC12A) family encodes membrane cation-coupled chloride cotransporters (CCCs), which are essential for ion transport and cellular homeostasis. By regulating intracellular chloride and potassium concentrations, SLC12A/CCC transporters may directly influence myocardial electrophysiology, repolarization dynamics, and susceptibility to cardiomyopathies. Dysfunction of potassium-handling cotransporters can disrupt action potential propagation, increasing the risk of arrhythmias, while chloride transport abnormalities exacerbate ischemic injury by impairing cell volume regulation and metabolic responses to hypoxia. This review examines the expression and protein levels of SLC12A/CCC cotransporters in cardiac tissue, providing crucial insights into their functional significance in maintaining cardiac ion homeostasis. Understanding the regulatory mechanisms of these transporters could inform therapeutic interventions to restore ion balance and mitigate myocardial dysfunction in affected patients, thereby improving cardiac health.

The solute carrier family 12A (SLC12A) superfamily of membrane transporters modulates the movement of cations coupled with chloride across the membrane. In doing so, these cotransporters are involved in numerous aspects of human physiology: cell volume regulation, ion homeostasis, blood pressure regulation, and neurological action potential via intracellular chloride concentration modulation. Their physiological characterization has been largely studied; however, understanding the mechanics of their function and the relevance of structural domains or specific amino acids has been a pending task. In recent years, single-particle cryogenic electron microscopy (cryo-EM) has been successfully applied to members of the SLC12A family including all K⁺:Cl⁻ cotransporters (KCCs), Na⁺:K⁺:2Cl⁻ cotransporter NKCC1, and recently Na⁺:Cl⁻ cotransporter (NCC); revealing structural elements that play key roles in their function. The present review analyzes the data provided by these cryo-EM reports focusing on structural domains and specific amino acids involved in ion binding, domain interactions, and other important SCL12A structural elements. A comparison of cryo-EM data from NKCC1 and KCCs is presented in the light of the two recent NCC cryo-EM studies, to propose insight into structural elements that might also be found in NCC and are necessary for its proper function. In the final sections, the importance of key coordination residues for substrate specificity and their implication on various pathophysiological conditions and genetic disorders is reviewed, as this could provide the basis to correlate structural elements with the development of novel and selective treatments, as well as mechanistic insight into the function and regulation of cation-coupled chloride cotransporters (CCCs).

Caveolae-associated signaling toward mitochondria contributes to the cardioprotective mechanisms against ischemia-reperfusion (I/R) injury induced by ischemic postconditioning. In this work, we evaluated the role that the actin-cytoskeleton network exerts on caveolae-mitochondria communication during postconditioning. Isolated rat hearts subjected to I/R and to postconditioning were treated with latrunculin A, a cytoskeleton disruptor. Cardiac function was compared between these hearts and those exposed only to I/R and to the cardioprotective maneuver. Caveolae and mitochondria structures were determined by electron microscopy and maintenance of the actin-cytoskeleton was evaluated by phalloidin staining. Caveolin-3 and other putative caveolae-conforming proteins were detected by immunoblot analysis. Co-expression of caveolin-3 and actin was evaluated both in lipid raft fractions and in heart tissue from the different groups. Mitochondrial function was assessed by respirometry and correlated with cholesterol levels. Treatment with latrunculin A abolishes the cardioprotective postconditioning effect, inducing morphological and structural changes in cardiac tissue, reducing F-actin staining and diminishing caveolae formation. Latrunculin A administration to post-conditioned hearts decreases the interaction between caveolae-forming proteins, the co-localization of caveolin with actin and inhibits oxygen consumption rates in both subsarcolemmal and interfibrillar mitochondria. We conclude that actin-cytoskeleton drives caveolae signaling to mitochondria during postconditioning, supporting their functional integrity and contributing to cardiac adaption against reperfusion injury.