Acid-Sensing Ion Channels Structural Aspects, Pathophysiological Importance and Experimental Mutational Data Available Across Various Species to Target Human ASIC1

Rubbing Salt in the Wound: Molecular Evolutionary Analysis of Pain-Related Genes Reveals the Pain Adaptation of Cetaceans in Seawater

Pain, usually caused by a strong or disruptive stimulus, is an unpleasant sensation that serves as a warning to organisms. To adapt to extreme environments, some terrestrial animals have evolved to be inherently insensitive to pain. Cetaceans are known as supposedly indifferent to pain from soft tissue injury representatives of marine mammals. However, the molecular mechanisms that explain how cetaceans are adapted to pain in response to seawater environment remain unclear. Here, we performed a molecular evolutionary analysis of pain-related genes in selected representatives of cetaceans. ASIC4 gene was identified to be pseudogenized in all odontocetes (toothed whales) except from Physeter macrocephalus (sperm whales), and relaxed selection of this gene was detected in toothed whales with pseudogenized ASIC4. In addition, positive selection was detected in pain perception (i.e., ASIC3, ANO1, CCK, and SCN9A) and analgesia (i.e., ASIC3, ANO1, CCK, and SCN9A) genes among the examined cetaceans. In this study, potential convergent amino acid substitutions within predicted proteins were found among the examined cetaceans and other terrestrial mammals, inhabiting extreme environments (e.g., V441I of TRPV1 in cetaceans and naked mole rats). Moreover, specific amino acid substitutions within predicted sequences of several proteins were found in the studied representatives of cetaceans (e.g., F56L and D163A of ASIC3, E88G of GRK2, and F159L of OPRD1). Most of the substitutions were located within important functional domains of proteins, affecting their protein functions. The above evidence suggests that cetaceans might have undergone adaptive molecular evolution in pain-related genes through different evolutionary patterns to adapt to pain, resulting in greater sensitivity to pain and more effective analgesia. This study could have implications for diagnosis and treatment of human pain.

Hydrogen Ion Dynamics as the Fundamental Link between Neurodegenerative Diseases and Cancer: Its Application to the Therapeutics of Neurodegenerative Diseases with Special Emphasis on Multiple Sclerosis

The pH-related metabolic paradigm has rapidly grown in cancer research and treatment. In this contribution, this recent oncological perspective has been laterally assessed for the first time in order to integrate neurodegeneration within the energetics of the cancer acid-base conceptual frame. At all levels of study (molecular, biochemical, metabolic, and clinical), the intimate nature of both processes appears to consist of opposite mechanisms occurring at the far ends of a physiopathological intracellular pH/extracellular pH (pHi/pHe) spectrum. This wide-ranging original approach now permits an increase in our understanding of these opposite processes, cancer and neurodegeneration, and, as a consequence, allows us to propose new avenues of treatment based upon the intracellular and microenvironmental hydrogen ion dynamics regulating and deregulating the biochemistry and metabolism of both cancer and neural cells. Under the same perspective, the etiopathogenesis and special characteristics of multiple sclerosis (MS) is an excellent model for the study of neurodegenerative diseases and, utilizing this pioneering approach, we find that MS appears to be a metabolic disease even before an autoimmune one. Furthermore, within this paradigm, several important aspects of MS, from mitochondrial failure to microbiota functional abnormalities, are analyzed in depth. Finally, and for the first time, a new and integrated model of treatment for MS can now be advanced.

Impairment of proprioceptive movement and mechanical nociception in Drosophila melanogaster larvae lacking Ppk30, a Drosophila member of the Degenerin/Epithelial Sodium Channel family

The mechanosensory neurons of Drosophila larvae are demonstrably activated by diverse mechanical stimuli, but the mechanisms underlying this function are not completely understood. Here we report a genetic, immunohistochemical, and electrophysiological analysis of the Ppk30 ion channel, a member of the Drosophila pickpocket (ppk) family, counterpart of the mammalian Degenerin/Epithelial Na⁺ Channel family. Ppk30 mutant larvae displayed deficits in proprioceptive movement and mechanical nociception, which are detected by class IV sensory (mdIV) neurons. The same neurons also detect heat nociception, which was not impaired in ppk30 mutant larvae. Similarly, Ppk30 mutation did not alter gentle touch mechanosensation, a distinct mechanosensation detected by other neurons, suggesting that Ppk30 has a functional role in mechanosensation in mdIV neurons. Consistently, Ppk30 was expressed in class IV neurons, but was not detectable in other larval skin sensory neurons. Mutant phenotypes were rescued by expressing Ppk30 in mdIV neurons. Electrophysiological analysis of heterologous cells expressing Ppk30 did not detect mechanosensitive channel activities, but did detect acid-induced currents. These data show that Ppk30 has a role in mechanosensation, but not in thermosensation, in class IV neurons, and possibly has other functions related to acid response.