Biology subjects

Akimoto, M.

Publications and source records attributed to Akimoto, M..

4 recordsLinked to original sources

bioRxiv2026

Follistatin improves vascular function by inhibiting oxidative stress and inducing browning of perivascular adipose tissue in essential hypertension

BackgroundEssential hypertension, characterized by vascular dysfunction, remains a leading modifiable cause of death globally. Perivascular adipose tissue (PVAT), which normally reduces vasoconstriction, becomes less anticontractile in hypertension due at least in part to increased reactive oxygen species (ROS). Brown PVAT has emerged as a protective regulator of vascular tone. Follistatin, an activin antagonist, induces browning of peripheral adipose tissue depots via AMPK. We recently reported improved blood pressure, vascular function and reduced vascular ROS by follistatin in the spontaneously hypertensive rat (SHR) model of essential hypertension. Here, we investigate whether follistatin reduces ROS and induces browning in SHR PVAT to restore PVAT function. MethodsSHR were treated with vehicle, follistatin or hydralazine for 8 weeks. Mesenteric white and thoracic brown PVAT from SHR and normotensive Wistar-Kyoto were utilized, with wire myography used to assess vascular function. Nitric oxide (NO) and nitrite were measured in PVAT using DAF-2 FM fluorescence or Griess reagent, respectively. PVAT ROS and browning markers were assessed biochemically and via immunohistochemistry. PVAT was treated ex vivo for 3 days to assess mechanisms of browning. Unbiased proteomic analysis of PVAT was performed using liquid chromatography-mass spectrometry. ResultsSHR PVAT dysfunction, manifest as a pro-contractile effect, was inhibited by follistatin through reducing ROS, enhancing NO bioavailability and inducing browning. Activin neutralization and AMPK phosphorylation mediated the beneficial effect of follistatin on SHR PVAT. Hydralazine-induced blood pressure reduction did not replicate follistatin effects, suggesting vascular benefits of follistatin are mediated by direct PVAT modulation. Proteomic analysis showed that follistatin shifts PVAT proteome towards normal state, upregulating processes associated with adipose tissue browning. ConclusionFollistatin restores PVAT-mediated vascular relaxation via ROS reduction, activin neutralization and AMPK-dependent browning, positioning the potential for PVAT as a therapeutic target for vascular dysfunction in essential hypertension.

physiology↗

bioRxiv2022

An auto-inhibited state of protein kinase G and implications for selective activation

Cyclic GMP-dependent protein kinases (PKGs) are key mediators of the nitric oxide/cGMP signaling pathway that regulates biological functions as diverse as smooth muscle contraction, cardiac function, and axon guidance. Campaigns targeting nitric oxide synthases and cyclic nucleotide phosphodiesterases in this signaling axis suggest that understanding how cGMP differentially triggers mammalian PKG isoforms could lead to new therapeutics that inhibit or activate PKGs. Alternate splicing of PRKG1 transcripts confers distinct leucine zippers, linkers, and auto-inhibitory pseudo-substrate sequences to PKG I and I{beta} that result in isoform-specific activation properties, but the mechanism of enzyme auto-inhibition and its alleviation by cGMP is still not well understood. Here we present a crystal structure of PKG I{beta} in which the auto-inhibitory sequence and the cyclic nucleotide binding domains are bound to the catalytic domain, providing a snapshot of the auto-inhibited state. Specific contacts between the PKG I{beta} auto-inhibitory sequence and the enzyme active site help explain isoform-specific activation constants and the effects of phosphorylation in the linker. We also present a crystal structure of a PKG I cyclic nucleotide binding domain with an activating mutation linked to Thoracic Aortic Aneurysms and Dissections. Similarity of this structure to wild type cGMP-bound domains and differences with the auto-inhibited enzyme provide a mechanistic basis for constitutive activation. We show that PKG I{beta} auto-inhibition is mediated by contacts within each monomer of the native full-length dimeric protein, and using the available structural and biochemical data we develop a model for the regulation and activation of PKGs.

biochemistry↗

bioRxiv2020

Mechanism of hERG inhibition by gating-modifier toxin, APETx1, deduced by functional characterization

Human ether-a-go-go-related gene potassium channel 1 (hERG) is a voltage-gated potassium channel, the voltage-sensing domain (VSD) of which is targeted by a gating-modifier toxin, APETx1. Although it is known that APETx1 inhibits hERG by stabilizing the resting state, it remains unclear where and how APETx1 interacts with the VSD in the resting state. Here, we prepared a recombinant APETx1, which is structurally and functionally equivalent to the natural product. Electrophysiological analyses using wild type and mutants of APETx1 and hERG revealed that their hydrophobic residues, in addition to a previously reported acidic hERG residue, play key roles in the inhibition of hERG by APETx1. Docking models of the APETx1-VSD complex that satisfy the results of mutational analysis suggest a molecular recognition mode between APETx1 and the resting state of hERG; this would provide a structural basis for designing ligands that control hERG function by binding to the VSD.

molecular biology↗

bioRxiv2019

Characterization and function of medium and large extracellular vesicles from plasma and urine by surface antigens and Annexin V

Medium/large extracellular vesicles (m/lEVs) are released by most cell types and are involved in multiple basic biological processes. Analysis of m/lEV levels in blood or urine may help unravel pathophysiological findings in many diseases. However, it remains unclear how many naturally-occurring m/lEV subtypes exist as well as how their characteristics and functions differ from one another. Here, we identified m/lEVs pelleted from plasma and urine samples by differential centrifugation and showed by flow cytometry that they typically possessed diameters between 200 nm and 800 nm. Using proteomic profiling, we identified several proteins involved in m/lEV biogenesis including adhesion molecules, peptidases and exocytosis regulatory proteins. In healthy human plasma, we could distinguish m/lEVs derived from platelets, erythrocytes, monocytes/macrophages, T and B cells, and vascular endothelial cells using various surface antigens. m/lEVs derived from erythrocytes and monocytes were Annexin V positive. In urine, 50% of m/lEVs were Annexin V negative but contained various membrane peptidases derived from renal tubular villi. Urinary m/lEVs, but not plasma m/lEVs, showed peptidase activity. The method we have developed to characterize cell-derived m/lEVs suggests the possibility of clinical applications.

molecular biology↗