Biology subjects

Siveke, I.

Publications and source records attributed to Siveke, I..

3 recordsLinked to original sources

bioRxiv2025

Constitutive activity of the inhibitory G protein pathway mediated by non-visual opsin Opn7b reduces cFos activity in stress and fear circuits and modulates avoidance behavior

Constitutive activity of G protein-coupled receptors (GPCRs) plays an important role in brain function and disease including neurodegenerative and psychiatric disorders. The non-visual opsin Opn7b is a constitutively active Gi/o coupled GPCR which has been used to synchronize neuronal networks. Here we show that expression of Opn7b in the bed nucleus of the stria terminalis and the ventral tegmental area, two interconnected brain areas involved in modulating fear and stress responses, reduces the number of cFos positive neurons and modulates avoidance behavior in mice. Thus, by constitutively activating the Gi/o pathway Opn7b can be used as a tool to reduce cFos expression and to link cFos-expressing neurons to network- and pathway-specific behavior.

neuroscience↗

bioRxiv2025

Multimodal characterization and optogenetic potential of the bistable Gi/o-coupled vertebrate ancient opsin from the flashlight fish Anomalops katoptron

Vertebrate ancient long opsin, or VAL opsin, is a light-sensitive protein that is found within and outside the visual system in vertebrates. In accordance with its wide distribution in the retina, brain, testis and skin, VAL is suggested to play a role in light-dependent physiological processes that are beyond vision. However, many aspects of the physiological properties and specific functions of VAL remain unclear. Here we identified and characterized the VAL opsin from the flashlight fish Anomalops katoptron (AkVAL) and show that this opsin is bistable and reversibly converts between active and inactive states by responding to cycles of green and blue/UV lights. We further show that AkVAL couples to the Gi/o pathway and controls the activity of GIRK channels in a bistable manner. In line with this, we demonstrated that AkVAL modulates neuronal activity in cerebellar Purkinje cells, where neuronal activity is reduced by UV/blue light and increased by green/red light illumination. In addition, upon the in vivo expression of AkVAL in neurons innervating body muscles of Caenorhabditis elegans the worms body movement can be bidirectionally controlled altering blue/UV and green illuminations. These data highlight the potential of AkVAL as an optogenetic tool to control cells in vitro and in vivo, in a bistable manner.

neuroscience↗

bioRxiv2025

Guiding G protein signaling by target enhancement of GPCRs

Activation of G protein coupled receptors coupling to the Gi/o pathway leads to the activation of G protein-activated inward rectifier potassium channels (GIRK) in a fast membrane-delimited manner in excitable cells. Activation of GIRK causes the hyperpolarization of the cell membrane, where hyperpolarization is dependent on te availability of Gi/o coupled GPCRs and GIRK. In particular, in optogenetic and chemogenetic experiments neuronal silencing depends on downstream targets of Gi/o-coupled GPCRs. To selectively enhance Gi/o mediated GIRK currents, we created expression cassettes consisting of a homomer forming GIRK subunit and various light-activated Gi/o-coupled GPCRs (Melanopsin, Long-wave-sensitive opsin 1, Parapinopsin or Opsin 7b). We demonstrate that light-activation of the GIRK/GPCR constructs induces robust GIRK currents in human embryonic kidney 293 cells, cardiomyocytes and cerebellar Purkinje cells and changes the net effect of G protein signaling of the promiscuous Opn4L from a Gq/11 mediated excitation towards an Gi/o mediated inhibition. Thus, our tools enhance target selectivity and improve optogenetic control of the Gi/o pathway by light in excitable cells.

neuroscience↗