Acta Physiologica, Journal Year: 2024, Volume and Issue: 240(2)
Published: Jan. 1, 2024
In this issue of Acta Physioloigica, Quijada-Rodriguez and colleuges1 artfully combine empirical evidence with a suite investigative tools to explore the dual capacity Crustacean Rh1 (CmRh1) protein as NH3 CO2 channel in European green crab (Carcinus maenas). Life is complex balance biochemical processes, regulation ammonia critical for homeostasis aquatic organisms. Both are natural waste products cellular metabolism, yet their accumulation within tissues can be detrimental function overall physiology. Due its small molecular size, traditional views transmembrane NH3/NH4+ transport propose (i) passive, gradient-driven diffusion gaseous across lipid membranes (ii) mediated movement ionic NH4+ through promiscuous via K+ channel/transporters, although most occurs at physiological pH. However, paradigm radically shifted discovery bacterial Amt/Met ammonium transporters closely related family Rh glycoproteins. First identified 1939 connection severe case post-stillborn spousal blood transfusion rejection2; it was only recently that glycoproteins (a.k.a. SLC42 solute-linked carriers) were characterized facilitators.3 Since then, they have been proven player implicated wide array roles indications, such chronic kidney disease renal tubular acidosis. The interplay between other putative acid/base/ion exemplified by “metabolon”—a multi-protein includes proteins Na+/H+ exchangers (NHEs) proposed help energize Na+ uptake freshwater teleosts,4 NHEs themselves also being posited potential facilitators transport,5 further upending previously held on beyond pathways. Like ammonia, has long considered passive process identity specific remains elusive even somewhat contentious. Previous studies hinted involvement mammals,6 fishes,7 corals algae.8, 9 Despite Rhp1 among first homologs cloned organisms,10 now et al.1 recent contribution bring light multiple isoform protein, not excretion, but perhaps excretion well. colleagues do claim role transport.6 stands out comprehensive use both classical modern comparative approaches. To address hypothesis dual-function employed techniques including cloning site-directed mutagenesis, complementation, radiolabeled flux experiments using heterologous expression yeast Xenopus oocytes. Additionally, utilized qPCR, Western blotting, immunostaining thoroughly investigate expressional patterns. authors focus Rh-like homolog from utilization cross-species phylogenetic analysis superfamily serves purpose study. Initially, categorize target, CmRh1, subfamily—a group linked swimming (Portunus trituberculatus) Si 2018.11 More critically, delineate various animal isoforms superfamily, identifying those known able and/or CO2. This tree emphasizes functions these underscores nascent state research into family. Through functional assays wild-type CmRh1 oocytes, demonstrate capacity. Most importantly, show convincingly abolished when oocytes instead injected mutant form (D180N) , site important substrate binding. qPCR analysis, predominantly expressed gills C. maenas, notable differences anterior posterior gills. Specifically, blotting reveals an enriched anti-CmRh1 signal They observe exposure high PCO2 levels (3 mmHg) leads reduction mRNA gills, while no significant changes noted A similar, albeit less pronounced, attenuation gill response environmental (HEA). Furthermore, patterns reveal apical localization Rh, corresponding membrane-bound carbonic anhydrase (CA) cells abundant Na+/K+-ATPase (NKA). Given dynamics transcriptional HEA, plausible dynamic shifts result subcellular re-organizations expression, removed membrane regulate inward ammonia. Such reorganization demonstrated highly ammonia-tolerant hagfish (Eptatretus stoutii) stark reductions HEA.5 Taken together, results two indicate external HEA cell surface, hint existence some sensing mechanism, which elucidated. Earlier algal (Chlamydomonas reinhardtii) variants successfully elevated CO2.9 While colleagues1 unable any responses immunoblotting, crucial caveat whole-animal experiment limited single time-point exposures. singular temporal may fully capture nature response, thus, possibility exists respond differently over time compared HEA. Clearly, detailed future would offer valuable insights adaptive mechanisms recovery processes Crustaceans (or hagfish) Moving forward, path forward clear: deeper dive protein-mediated essential. exploration must extend diverse range species, current study's framework roadmap confirm or disconfirm universality life. conclusion, al.'s study step toward unraveling capacities physiology, should encourage examination taxa. Overall, sets stage subsequent will undoubtedly refine our understanding intricate management. Alexander M. Clifford: Conceptualization; writing – original draft; review editing; investigation. There relevant acknowledgements article. author declares conflict interest. Data sharing applicable article datasets generated analysed during
Language: Английский