A jellyfish model to study optogenetics

Box jellyfish, an ancient invertebrate species, have evolved separately from vertebrates for more than 500 million years. Unlike other jellyfish species, box jellyfish have well-developed eyes similar to vertebrates. These eyes have light-sensitive protein receptors called rhodopsins, which allow them to process visual cues such as twilight and color perception, which are essential for survival.

Shino Inukai, Kota Katayama, Hideki Kandori and colleagues at Nagoya Institute of Technology discovered that jellyfish rhodopsin is similar to vertebrate rhodopsin. In a recent article published in biochemistry journalThey describe the structural similarities, photoresponsive activity, and highly developed visual functions of rhodopsin in box jellyfish and vertebrates.

Box jellyfish have the only animal rhodopsin known to activate Gs proteins. G proteins are guanine nucleotide binding proteins. They transmit signals from receptors on the cell surface to the interior of the cell, where they regulate a wide range of cellular functions and processes. These include maintaining cellular homeostasis, response to external stimuli, neurotransmission, and sensory perception.

Box jellyfish rhodopsin (JelRh) is the only animal rhodopsin that researchers have shown to transduce the G-protein signaling pathway. Jellyfish rhodopsin is a promising new optogenetic tool because it can control G protein signaling pathways by light.

The authors used JelRh to study how G proteins control cyclic adenosine monophosphate induction (cAMP), which is widely associated with biological processes such as circadian rhythms, cardiac function, and behavioral control. did. In the authors’ words: “The development of jellyfish rhodopsin can be used as a tool to elucidate the molecular mechanisms of diseases caused by aberrant signaling through Gs proteins, such as nephrogenic diabetes insipidus and obesity.” That’s what it means.

Although the study shows promising results, the authors acknowledge that the model has certain limitations. The authors’ discovery of a distinctive hydrogen bond network in JelRh surrounding the retinal chromophore suggests differences in the intermediate structure of rhodopsin in other invertebrates and vertebrates.

Researchers have not yet characterized other important defining factors of JelRh. Therefore, the authors suggest future work to perform site-directed mutagenesis measurements to determine important residues in GPCR activation. Future structural studies will focus on the active state photoreaction and investigate how JelRh triggers the Gs protein-mediated phototransduction cascade. Specifically, spectroscopy-based structural studies of the photoresponse dynamics of Gs-coupled animal rhodopsin provide insight into the activation mechanism of G protein-coupled receptors.

Looking ahead, the research team proposes to elucidate the photoactivation and signal transduction mechanisms of JelRh, the only animal rhodopsin proven to transmit Gs signals. Specifically, we aim to decipher the molecular complexity underlying the activation of Gs proteins.

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