Biology subjects

Taki, S.

Publications and source records attributed to Taki, S..

3 recordsLinked to original sources

bioRxiv2025

Role of channels in the O2 permeability of murine red blood cells II. Morphological and proteomic studies

In this second of three papers, we examine red blood cell (RBC) morphometry and RBC-membrane proteomics from our laboratory mouse strain (C57BL/6Case). In paper #1, using stopped-flow absorbance spectroscopy to ascertain the rate constant for oxyhemoglobin (HbO2) deoxygenation (kHbO2), we find substantial kHbO2 reductions with (1) membrane-protein inhibitors p-chloromercuribenzenesulfonate (pCMBS) or 4,4-diisothiocyanatostilbene-2,2-disulfonate (DIDS); (2) knockouts of aquaporin-1 (AQP1-KO), or Rhesus blood-group-associated A-glycoprotein (RhAG-KO), or double knockouts (dKO); or (3) inhibitor+dKO. In paper #3, reaction-diffusion mathematical modeling/simulations reveal that kHbO2 could fall secondary to slowed intracellular O2/HbO2/Hb diffusion. Here in paper #2, blood smears as well as still/video images and imaging flow cytometry (IFC) of living RBCs show that [~]97.5% to [~]98.6% of control (not drug-treated) cells are biconcave disks (BCDs) across all genotypes. Pretreatment with pCMBS raises non-BCD abundance to [~]8.7% for WT and [~]5.7% for dKO; for DIDS pretreatment, the figures are [~]41% and [~]21%, respectively. Modeling (paper #3) accommodates for these shape changes. Light-scattering flow cytometry shows no significant difference in RBC size or shape among genotypes. IFC reveals minor differences among genotypes in RBC major diameter (OMajor), which (along with mean corpuscular volume, paper #1) yields RBC thickness for simulations in paper #3. Label-free liquid chromatography/tandem mass spectrometry (LC/MS/MS) proteomic analyses of RBC plasma-membrane ghosts confirm the deletion of proteins targeted by our knockouts, and rule out changes in the 100 proteins of greatest inferred abundance. Thus, genetically induced changes in kHbO2 must reflect altered abundance of AQP1 and /or the Rh complex. Key PointsO_LIO2-offloading from red blood cells (RBCs) depends not only on membrane O2 permeability and oxyhemoglobin dissociation, but also on RBC size and shape. In this second of three papers, we use blood smears, still/video images of living RBCs, and imaging flow cytometry to examine morphometry of RBCs from paper #1. C_LIO_LIWe find that mouse RBCs of all genotypes--wild-type, aquaporin-1 knockout (AQP1-KO), Rhesus blood group-associated A-glycoprotein knockout (RhAG-KO), and double knockout--are dominantly biconcave discs, with [~]1.4% to [~]2.5% poikilocytosis (shape change, SC). Drug pre-treatment increases %SC. C_LIO_LIUsing label-free liquid chromatography/tandem mass spectrometry to assess apparent abundance of RBC-ghost proteins, we find no significant differences among genotypes for any of the [~]100 most abundant protein species except, as appropriate, AQP1, RhAG, or Rhesus blood group D antigen. C_LIO_LIThus, the substantial effects observed in paper #1 cannot be attributed to differences in morphometry or protein content. C_LI

physiology↗

bioRxiv2024

Possible involvement of ghost introgressions in the striking diversity of V1R receptor genes in East African cichlids

Cichlids that have undergone adaptive radiation are genetically close but exhibit extreme ecological and morphological diversity, making them useful for understanding speciation mechanisms. Vomeronasal type 1 receptors (V1R) are highly conserved among teleost fish at the amino acid sequence level and believed to play a fundamental role in reproduction. We previously reported the surprisingly high sequence diversity of V1Rs among certain cichlid species, suggesting a possible role for V1Rs in their speciation. In this study, we investigated the process of evolutionary diversification of all 6 V1Rs (V1R1-6) by using the genome data of 528 cichlid species, encompassing nearly all lineages. In the case of V1R2, two highly divergent alleles (1.17%: variant sites/CDS length) without recombination were preserved and shared among cichlids found in all of the East African Great Lakes. In the case of V1R6, numerous highly variable alleles that could be derived from multiple recombination events between two highly divergent alleles (1.39%: variant sites/CDS length) were found among the Lake Victoria cichlids. Additionally, we identified highly divergent alleles of V1R1 within the tribe Tropheini, and of both V1R3 and V1R6 within Trematocarini and Ectodini. Because one of the two divergent alleles of these V1Rs emerged rapidly during cichlid evolution, they are likely to have been derived from introgression. However, despite extensive investigations, we could not identify the source lineages for these introgressions, implying that they may have become extinct. This study revealed the potential role of introgression in explaining the remarkable diversity of V1Rs in East African cichlids.

evolutionary biology↗

bioRxiv2020

Role of channels in the oxygen permeability of red blood cells

Many have believed that oxygen (O2) crosses red blood cell (RBC) membranes by dissolving in lipids that offer no resistance to diffusion. However, using stopped-flow (SF) analyses of hemoglobin (Hb) absorbance spectra during O2 off-loading from mouse RBCs, we now report that most O2 traverses membrane-protein channels. Two agents excluded from the RBC interior markedly slow O2 off-loading: p-chloromercuribenzenesulfonate (pCMBS) reduces inferred membrane O2 permeability (PMembrane) by [~]82%, and 4,4-diisothiocyanatostilbene-2,2-disulfonate (DIDS), by [~]56%. Because neither likely produces these effects via membrane lipids, we examined RBCs from mice genetically deficient in aquaporin-1 (AQP1), the Rh complex (i.e., rhesus proteins RhAG + mRh), or both. The double knockout (dKO) reduces PMembrane by [~]55%, and pCMBS+dKO, by [~]91%. Proteomic analyses of RBC membranes, flow cytometry, hematology, and mathematical simulations rule out explanations involving other membrane proteins, RBC geometry, or extracellular unconvected fluid (EUF). By identifying the first two O2 channels and pointing to the existence of other O2 channel(s), all of which could be subject to physiological regulation and pharmacological intervention, our work represents a paradigm shift for O2 handling.

physiology↗