Physiological reviews最新文献

In 2005, the Arabidopsis thaliana two-pore channel TPC1 channel was identified as a vacuolar Ca^²⁺-release channel. In 2009 three independent groups published studies on mammalian TPCs as NAADP-activated endolysosomal Ca²⁺ release channels, results that were eventually challenged by two other groups, claiming mammalian TPCs to be PI(3,5)P₂ activated Na⁺ channels. By now this dispute seems to have been largely reconciled. Lipophilic small molecule agonists of TPC2, mimicking either the NAADP or the PI(3,5)P₂ mode of channel activation, revealed, together with structural evidence, that TPC2 can change its selectivity for Ca²⁺ versus Na⁺ in a ligand-dependent fashion (N- versus P-type activation). Furthermore, NAADP-binding proteins, JPT2 and Lsm12 were discovered, corroborating the hypothesis that NAADP activation of TPCs only works in the presence of these auxiliary NAADP-binding proteins. Pathophysiologically, loss or gain of function of TPCs has effects on autophagy, exocytosis, endocytosis, and intracellular trafficking, e.g., LDL cholesterol trafficking leading to fatty liver disease or viral and bacterial toxin trafficking, corroborating roles of TPCs in infectious diseases such as Ebola or Covid19. Defects in trafficking of EGFR and 1-integrin suggested roles in cancer. In neurodegenerative lysosomal storage disease models, P-type activation of TPC2 was found to have beneficial effects on both in vitro and in vivo hallmarks of Niemann- Pick disease type C1, Batten disease, and Mucolipidosis type IV. Here, we cover the latest on structure, function, physiology, and pathophysiology of these channels with a focus initially on plant followed by mammalian TPCs, and we discuss their potential as drug targets, including currently available pharmacology.

At the simplest level, neurons are structured to integrate synaptic input and perform computational transforms on that input, converting it into an action potential (AP) code. This process, converting synaptic input into AP output, typically occurs in a specialized region of the axon termed the axon initial segment (AIS). The AIS, as its name implies, is often contained to the first section of axon abutted to the soma and is home to a dizzying array of ion channels, attendant scaffolding proteins, intracellular organelles, extracellular proteins, and, in some cases, synapses. The AIS serves multiple roles as the final arbiter for determining if inputs are sufficient to evoke APs, as a gatekeeper that physically separates the somatodendritic domain from the axon proper, and as a regulator of overall neuronal excitability, dynamically tuning its size to best suit the needs of parent neurons. These complex roles have received considerable attention from experimentalists and theoreticians alike. Here, we review recent advances in our understanding of the AIS and its role in neuronal integration and polarity in health and disease.

The 3',5'-cyclic adenosine monophosphate (cAMP) mediates the effects of sympathetic stimulation on the rate and strength of cardiac contraction. Beyond this pivotal role, in cardiac myocytes cAMP also orchestrates a diverse array of reactions to various stimuli. To ensure specificity of response, the cAMP signaling pathway is intricately organized into multiple, spatially confined, subcellular domains, each governing a distinct cellular function. In this review, we describe the molecular components of the cAMP signaling pathway with a specific focus on adenylyl cyclases, A-kinase anchoring proteins, and phosphodiesterases. We discuss how they are organized inside the intracellular space and how they achieve exquisite regulation of signaling within nanometer-size domains. We delineate the key experimental findings that lead to the current model of compartmentalized cAMP signaling, and we offer an overview of our present understanding of how cAMP nanodomains are structured and regulated within cardiac myocytes. Furthermore, we discuss how compartmentalized cAMP signaling is affected in cardiac disease and consider the potential therapeutic opportunities arising from understanding such organization. By exploiting the nuances of compartmentalized cAMP signaling, novel and more effective therapeutic strategies for managing cardiac conditions may emerge. Finally, we highlight the unresolved questions and hurdles that must be addressed to translate these insights into interventions that may benefit patients.