pubmed

Sea urchin histamine receptor 1 regulates programmed cell death in larval Strongylocentrotus purpuratus.

Latest Publications - Tue, 10/29/2019 - 14:39
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Sea urchin histamine receptor 1 regulates programmed cell death in larval Strongylocentrotus purpuratus.

Sci Rep. 2018 03 05;8(1):4002

Authors: Lutek K, Dhaliwal RS, Van Raay TJ, Heyland A

Abstract
Settlement is a rapid process in many marine invertebrate species, transitioning a planktonic larva into a benthic juvenile. In indirectly developing sea urchins, this ecological transition correlates with a morphological, developmental and physiological transition (metamorphosis) during which apoptosis is essential for the resorption and remodelling of larval and juvenile structures. While settlement is initiated by environmental cues (i.e. habitat-specific or benthic substrate cues), metamorphosis is regulated by developmental endocrine signals, such as histamine (HA), thyroid hormones (THs) and nitric oxide (NO). In the purple sea urchin, Strongylocentrotus purpuratus, we found that suH1R mRNA levels increase during larval development and peak during metamorphic competence. SuH1R positive cell clusters are prominently visible in the mouth region of sea urchin larvae, but the protein appears to be expressed at low levels throughout the larval arms and epidermis. SuH1R knock-down experiments in larval stages show that the function of suH1R is in inhibiting apoptosis. Our results therefore suggest that suH1R is regulating the metamorphic transition by inhibiting apoptosis. These results provide new insights into metamorphic mechanisms and have implications for our understanding of settlement and metamorphosis in the marine environment.

PMID: 29507306 [PubMed - indexed for MEDLINE]

Categories: pubmed

Toxigenic effects of two benthic diatoms upon grazing activity of the sea urchin: morphological, metabolomic and de novo transcriptomic analysis.

Latest Publications - Thu, 10/24/2019 - 14:35
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Toxigenic effects of two benthic diatoms upon grazing activity of the sea urchin: morphological, metabolomic and de novo transcriptomic analysis.

Sci Rep. 2018 04 04;8(1):5622

Authors: Ruocco N, Costantini S, Zupo V, Lauritano C, Caramiello D, Ianora A, Budillon A, Romano G, Nuzzo G, D'Ippolito G, Fontana A, Costantini M

Abstract
Diatoms are unicellular algae playing a key role as photosynthetic organisms in the world's ocean food webs. The chemical ecology of planktonic diatoms is well documented, but few studies have reported on the effects of benthic diatoms on their consumers, also due to difficulties in the collection, quantification and massive culturing of benthic species. Here for the first time we investigate the effects of feeding on two abundantly occurring benthic diatoms, Nanofrustulum shiloi and Cylindrotheca closterium, isolated from the leaves of the seagrass Posidonia oceanica, on the sea urchin Paracentrotus lividus. Adult P. lividus were fed for one month on diets of either one of the two diatoms and on the green alga Ulva rigida, used as a feeding control. By combining morphological, metabolomic and de novo transcriptomic approaches, we demonstrate toxigenic effect on embryos generated by females fed with these benthic diatoms. Furthermore, chemical analysis reveal the presence of polyunsaturated aldehydes only for N. shiloi, and a high production of other oxylipins (cytotoxic compounds on their grazers and on cancer cell lines) for both diatoms, including some additional peaks not correlated to the canonic oxylipins commonly observed in planktonic diatoms. These findings open new perspectives in the study of diatom secondary metabolites influencing their grazers.

PMID: 29618786 [PubMed - indexed for MEDLINE]

Categories: pubmed

Histidine168 is crucial for ΔpH-dependent gating of the human voltage-gated proton channel, hHV1.

Latest Publications - Tue, 10/01/2019 - 13:09
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Histidine168 is crucial for ΔpH-dependent gating of the human voltage-gated proton channel, hHV1.

J Gen Physiol. 2018 06 04;150(6):851-862

Authors: Cherny VV, Morgan D, Thomas S, Smith SME, DeCoursey TE

Abstract
We recently identified a voltage-gated proton channel gene in the snail Helisoma trivolvis, HtHV1, and determined its electrophysiological properties. Consistent with early studies of proton currents in snail neurons, HtHV1 opens rapidly, but it unexpectedly exhibits uniquely defective sensitivity to intracellular pH (pHi). The H+ conductance (gH)-V relationship in the voltage-gated proton channel (HV1) from other species shifts 40 mV when either pHi or pHo (extracellular pH) is changed by 1 unit. This property, called ΔpH-dependent gating, is crucial to the functions of HV1 in many species and in numerous human tissues. The HtHV1 channel exhibits normal pHo dependence but anomalously weak pHi dependence. In this study, we show that a single point mutation in human hHV1-changing His168 to Gln168, the corresponding residue in HtHV1-compromises the pHi dependence of gating in the human channel so that it recapitulates the HtHV1 response. This location was previously identified as a contributor to the rapid gating kinetics of HV1 in Strongylocentrotus purpuratus His168 mutation in human HV1 accelerates activation but accounts for only a fraction of the species difference. H168Q, H168S, or H168T mutants exhibit normal pHo dependence, but changing pHi shifts the gH-V relationship on average by <20 mV/unit. Thus, His168 is critical to pHi sensing in hHV1. His168, located at the inner end of the pore on the S3 transmembrane helix, is the first residue identified in HV1 that significantly impairs pH sensing when mutated. Because pHo dependence remains intact, the selective erosion of pHi dependence supports the idea that there are distinct internal and external pH sensors. Although His168 may itself be a pHi sensor, the converse mutation, Q229H, does not normalize the pHi sensitivity of the HtHV1 channel. We hypothesize that the imidazole group of His168 interacts with nearby Phe165 or other parts of hHV1 to transduce pHi into shifts of voltage-dependent gating.

PMID: 29743300 [PubMed - indexed for MEDLINE]

Categories: pubmed