Harter, TS, Sackville, M, Wilson, JM et al. (5 more authors) (2018) A solution to Nature's haemoglobin knockout: a plasma-accessible carbonic anhydrase catalyses CO₂ excretion in Antarctic icefish gills. Journal of Experimental Biology, 221 (22). jeb190918. ISSN 0022-0949
Abstract
In all vertebrates studied to date, CO₂ excretion depends on the enzyme carbonic anhydrase (CA) that catalyses the rapid conversion of HCO₃− to CO₂ at the gas-exchange organs. The largest pool of CA is present within red blood cells (RBC) and, in some vertebrates, plasma-accessible CA (paCA) isoforms participate in CO₂ excretion. However, teleost fishes typically do not have paCA at the gills and CO₂ excretion is reliant entirely on RBC CA; a strategy that is not possible in icefishes. As the result of a natural knockout, Antarctic icefishes (Channichthyidae) are the only known vertebrates that do not express haemoglobin (Hb) as adults, and largely lack RBC in the circulation (haematocrit<1%). Previous work has indicated the presence of high levels of membrane-bound CA activity in the gills of icefishes, but without determining its cellular orientation. Thus, we hypothesised that icefishes express a membrane-bound CA isoform at the gill that is accessible to the blood plasma. The CA distribution was compared in the gills of two closely-related notothenioid species, one with Hb and RBCs (Notothenia rossii) and one without (Champsocephalus gunnari). Molecular, biochemical and immunohistochemical markers indicate high levels of a Ca4 isoform in the gills of the icefish (but not the red-blooded N. rossii), in a plasma-accessible location that is consistent with a role in CO₂ excretion. Thus, in the absence of RBC CA, the icefish gill could exclusively provide the catalytic activity necessary for CO₂ excretion; a pathway that is unlike that of any other vertebrate.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | (c) 2018. Published by The Company of Biologists Ltd. This is an author produced version of a paper published in the Journal of Experimental Biology. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | notothenioid, teleost, adaptive radiation, PI-PLC, plasma CA inhibitor, Ca4 |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Biological Sciences (Leeds) > School of Biomedical Sciences (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 09 Oct 2018 14:07 |
Last Modified: | 05 Oct 2019 00:38 |
Status: | Published |
Publisher: | The Company of Biologists |
Identification Number: | 10.1242/jeb.190918 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:136503 |