Characterization of two isoforms of a novel ammonia transporter, LpHIAT1α and LpHIAT1β, in the American horseshoe crab Limulus polyphemus

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dc.contributor.authorEckhardt, Maria
dc.contributor.examiningcommitteeJeffries, Kenneth (Biological Sciences)en_US
dc.contributor.examiningcommitteeAnderson, W. Gary (Biological Sciences)en_US
dc.contributor.supervisorWeihrauch, Dirk
dc.date.accessioned2022-09-23T15:35:00Z
dc.date.available2022-09-23T15:35:00Z
dc.date.copyright2022-09-21
dc.date.issued2022-09-20
dc.date.submitted2022-09-21T19:38:16Zen_US
dc.degree.disciplineBiological Sciencesen_US
dc.degree.levelMaster of Science (M.Sc.)en_US
dc.description.abstractThe American horseshoe crab, Limulus polyphemus, excretes nitrogenous waste in the form of highly toxic ammonia across their book gills. The mechanism of this branchial excretion is yet unknown. In another marine arthropod, the green crab Carcinus maenas, a novel ammonia transporter has been discovered and shown to be expressed in the gills. In the current study, two isoforms of this transporter, LpHIAT1α and LpHIAT1β, have been identified in L. polyphemus. Both isoforms have 12 predicted transmembrane regions and share 82.7% of amino acid identity to each other. Significantly higher mRNA expression levels of LpHIAT1α were observed in the peripheral mitochondria-poor region of the gill (PMPA), central mitochondria-rich region of the gill (CMRA), and in the brain compared to the LpHIAT1β isoform. Heterologous expression of LpHIAT1α and LpHIAT1β in Xenopus laevis oocytes resulted in a significantly lower uptake of the radiolabeled ammonia analogue 3H-methylamine compared to water-injected control oocytes, suggesting an excretory function of this transporter. Exposure to elevated environmental ammonia (HEA, 1 mmol l-1) caused an increase in mRNA expression of LpHIAT1β in the ion-conductive ventral gill half. The high mRNA expression of both isoforms in the brain, and the LpHIAT1α- and LpHIAT1β-mediated methylamine excretion suggest that these highly conserved ammonia transporters have an imperative protective function in cellular ammonia detoxification.en_US
dc.description.noteFebruary 2023en_US
dc.identifier.urihttp://hdl.handle.net/1993/36921
dc.language.isoengen_US
dc.rightsopen accessen_US
dc.subjectFunctional expressionen_US
dc.subjectOocyteen_US
dc.subjectMfsd14en_US
dc.subjectHigh environmental ammoniaen_US
dc.subjectChelicerataen_US
dc.titleCharacterization of two isoforms of a novel ammonia transporter, LpHIAT1α and LpHIAT1β, in the American horseshoe crab Limulus polyphemusen_US
dc.typemaster thesisen_US
local.subject.manitobanoen_US
project.funder.identifierhttps://doi.org/10.13039/501100000038en_US
project.funder.nameNatural Sciences and Engineering Research Council of Canadaen_US
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