![]() Ideally, optogenetic GPCRs should be selective for only one of the four major G protein classes. Thus optogenetics has been used to investigate GPCR signaling in cells 18, 19, 20, the heart 21, 22, the eye 23, 24, 25, and the brain 7, 19, 26, 27, 28, 29. The advantages of optogenetic stimulation are unprecedented temporal and spatial precision, cell-type-specific manipulations, and subcellular targeting. Optogenetics is a technique that allows to control cellular behavior with light after expressing light-sensitive proteins in cell-types of interest. However, the temporal encoding, subcellular compartmentalization, as well as microdomain discrimination is less understood since the tools to investigate G q signaling have been restricted to pharmacological or genetic approaches both lacking spatial and temporal precision 7. light, stretch, or depolarization 4, 16, 17. Over the past century, a lot of “binary” knowledge was gathered about mechanisms leading to activation or inactivation of GPCRs by drugs, hormones, transmitters, ions as well as physical stimuli, e.g. Since G q signaling plays a major role for the physiological adaption of cellular function it is also involved in the pathogenesis of a myriad of diseases 10 being key for platelet aggregation 11, synaptic plasticity 11, autoimmunity 12, cancerogenesis 13, 14, physiological as well as pathological cardiac growth and the development of heart failure 8, 11, 15. These include contraction of smooth muscle cells, regulation of contractility in cardiomyocytes 8, gene expression, posttranslational modification, and various other mechanisms in almost every cell type 9. The two-second messengers together with various other non-canonical pathways 6, 9, 10 control a plethora of different aspects of cellular function. ![]() DAG activates the protein kinase C and transient receptor potential channels (TRPC) 8 whereas IP 3 initiates the release of Ca 2+ ions from the endoplasmic reticulum 2, 6, 9. Once activated by the GPCR, G q α subunits trigger phospholipase Cβ (PLC-β) activity, which hydrolyses phosphatidylinositol-4,5-bisphosphate (PIP2) into diacylglycerol (DAG) and inositol 1,4,5 trisphosphate (IP 3). G q proteins are one of four major classes of G proteins 2 which can be subdivided according to the respective α subunits G q, G 11, G 14, and G 15/16 3, 6, 7. G protein coupled receptors (GPCRs) are the largest class of cell surface receptors and transform extracellular information into intracellular signaling for the regulation of enzymes, ion channels, transporters, and other components of the cellular machinery 1, 2, 3, 4, 5. Thus, we demonstrate specific G q signaling of hOPN5 and unveil its potential for optogenetic applications. All-optical high-throughput screening for TRPC6 inhibitors is more specific and sensitive than conventional pharmacological screening. In addition, we demonstrate light induced contractions in the small intestine, which are not detectable after pharmacological G q protein block. In adult hearts from a transgenic animal model, light increases the spontaneous beating rate. Properties and G protein specificity of hOPN5 are characterized by UV light induced IP 3 generation, Ca 2+ transients and inhibition of G IRK channel activity in HEK cells. ![]() Here we present the human Neuropsin (hOPN5) for specific and repetitive manipulation of G q signaling in vitro and in vivo with high spatio-temporal resolution. The underlying kinetics and transformation from extracellular stimuli into intracellular signaling, however could not be investigated in detail so far. G q proteins are universally important for signal transduction in mammalian cells.
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