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Arnolds, O.

Publications and source records attributed to Arnolds, O..

3 recordsLinked to original sources
bioRxiv2024

ABHD2 activity is not required for the non-genomic action of progesterone on human sperm

Study questionIs the hydrolase ABHD2 required for progesterone-induced Ca2+ influx via CatSper and the resulting motility responses in human sperm? Summary answerProgesterone-induced Ca2+ influx via CatSper and the resulting motility responses in human sperm do not require ABHD2 activity. What is known alreadySperm motility is tightly regulated by signalling pathways that are activated as sperm ascend the female reproductive tract, including progesterone triggering Ca2+ influx via the CatSper channel and inducing hyperactivated motility needed for fertilization. This process is thought to involve ABHD2, which may hydrolyse the endogenous CatSper inhibitor 2-arachidonoylglycerol (2-AG), thereby relieving inhibition and enabling calcium entry into the flagellum. Study design, size, durationPotent small molecule inhibitors of ABHD2 activity were synthesized, characterized, and used as tools to scrutinize the role of ABHD2 in activation of CatSper and regulation of sperm motility. Participants/materials, setting, methodsDerivatives of published ABHD2 inhibitors were optimised for in vitro potency and cellular activity and subsequently tested in human sperm motility and Ca2+ influx assays. Main results and the role of chanceProgesterone does not activate ABHD2 in vitro. In addition, inhibition of ABHD2 in human sperm has no effect on progesterone-induced Ca2+ influx through CatSper nor on basal or progesterone-induced hyperactivated motility. This demonstrates that ABHD2 activity is, in fact, not required for the non-genomic action of progesterone on human sperm. Large scale datanone Limitations, reasons for cautionWe examined the effects of inhibition of the enzymatic activity of ABHD2. We cannot exclude that ABHD2 functions as a part of a larger multiprotein complex, in which it may play a structural role independent of its hydrolase activity. Wider implications of the findingsThis study presents conclusive evidence that ABHD2 does not bind progesterone and that its hydrolase activity is not required for progesterone activation of CatSper and resulting changes in motility of human sperm. These results highlight the need for further research to elucidate the mechanism underlying the non-genomic action of progesterone on human sperm. Study funding/competing interest(s)This publication is based on research funded by the Gates Foundation. The findings and conclusions contained within are those of the authors and do not necessarily reflect positions or policies of the Gates Foundation. LT, CB, and TS were supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - project numbers 329621271 (CRU326; CB, TS), and 404595355 (Research Training Group "Chemical biology of ion channels (Chembion); LT, TS). This work was funded by the German Federal Ministry of Education and Research (BMBF) within the framework of Contraception Research, grant number 01GR2501A and 01GR2502A. A.A., K.V., A.T., N.D., A.H., M.W. and R.L. are employees of Nuvisan ICB GMBH, Berlin, Germany. Nuvisan is recipient of a Gates Foundation grant. A.A is associate editor of Human Reproduction Open.

cell biology↗
bioRxiv2022

A new fold in TANGO1 evolved from SH3 domains for the export of bulky cargos

Bulky cargos like procollagens, apolipoproteins, and mucins exceed the size of conventional COPII vesicles. During evolution a process emerged in metazoans, predominantly governed by the TANGO1 protein family, that organizes cargo at the exit sites of the endoplasmic reticulum and facilitates export by the formation of tunnel-like connections between the ER and Golgi. Cargorecognition appears to be mediated by an SH3-like domain, however, just how the vastly different cargos are recognized remains elusive. Based on structural and dynamic data as well as interaction studies from NMR spectroscopy presented here, we show that the luminal cargo-recognition domain of TANGO1 adopts a new functional fold for which we suggest the term MOTH (MIA, Otoraplin, TALI/TANGO1 homology) domain. Also, differences in the structural properties within the domain family suggest fundamentally different mechanisms of cargo-recognition in vertebrates and invertebrates. Similarly, in vertebrates, it is proposed that cargo-specificity is mediated by structural differences within the vertebrate TANGO1 and TALI MOTH domains themselves.

biophysics↗
bioRxiv2020

How to build a water-splitting machine: structural insights into photosystem II assembly

Biogenesis of photosystem II (PSII), natures water splitting catalyst, is assisted by auxiliary proteins that form transient complexes with PSII components to facilitate stepwise assembly events. Using cryo-electron microscopy, we solved the structure of such a PSII assembly intermediate with 2.94 [A] resolution. It contains three assembly factors (Psb27, Psb28, Psb34) and provides detailed insights into their molecular function. Binding of Psb28 induces large conformational changes at the PSII acceptor side, which distort the binding pocket of the mobile quinone (QB) and replace bicarbonate with glutamate as a ligand of the non-heme iron, a structural motif found in reaction centers of non-oxygenic photosynthetic bacteria. These results reveal novel mechanisms that protect PSII from damage during biogenesis until water splitting is activated. Our structure further demonstrates how the PSII active site is prepared for the incorporation of the Mn4CaO5 cluster, which performs the unique water splitting reaction. One Sentence HighlightThe high-resolution Cryo-EM structure of the photosystem II assembly intermediate PSII-I reveals how natures water splitting catalyst is assembled, protected and prepared for photoactivation by help of the three assembly factors Psb27, Psb28 and Psb34.

plant biology↗