Shining light on the functions of a brain non-visual opsin

• Grant number: 24/19300-9
• Support Opportunities: Regular Research Grants
• Start date: February 01, 2025
• End date: January 31, 2027
• Field of knowledge: Biological Sciences - Physiology - Physiology of Organs and Systems
• Mobility Program: SPRINT - Projetos de pesquisa - Mobilidade
• Principal Investigator: Andre de Souza Mecawi
• Grantee: Andre de Souza Mecawi
• Principal researcher abroad: David Murphy
• Institution abroad: University of Bristol, England
• Host Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil
• Associated research grant: 19/27581-0 - Control of vasopressin secretion in pregnancy and its implications in pathophysiology of Preeclampsia, AP.JP

Abstract

Synchronisation to periodic cues such as food/water availability and light/dark cycles is crucial for homeostasis. Modern lifestyles disturb our diurnal rhythms, most acutely by jetlag, but more insidiously by shift work and exposure to artificial light at night (ALAN), with consequential increased susceptibility of night-time workers to diabetes, obesity, cardiovascular disease and depression. This is a growing problem with an increasing number of people working in low paid night work. The daily transitions between sleep and arousal are regulated by internal and external cues, the most prominent of the latter being light. Exposure to artificial light, for example the blue light emitted by devices such as mobile phones, has been shown to negatively influence sleep. It is therefore essential to explore the mechanisms of light-regulated arousal in order to improve health and wellbeing. The extraretinal photoreceptor Opsin3 is a blue-light sensitive protein present in several brain regions, including the hypothalamus, with unknown roles. Interestingly, Opsin3 gene expression increases in the supraoptic nucleus (SON) of the hypothalamus in response to dehydration. The SON is part of a neurosecretory apparatus responsible for the production of the antidiuretic peptide hormone arginine vasopressin (AVP) and the reproductive and natriuretic peptide hormone oxytocin (OXT). The SON consists of two distinct populations of magnocellular neurones (MCNs) that separately synthesise either AVP or OXT. We have observed that Opsin3 is present in both AVP and OXT MCNs. Importantly, it has been shown that delivery of blue light into the SON in vivo promotes wakefulness by decreasing slow-wave sleep, suggesting that light may act directly on photoreceptors in deep brain structures can impact behaviour. We hypothesise that these light-dependent events are mediated by Opsin3. We hypothesise that OPN3 regulates magnocellular neurone activity-secretion coupling and consequently modulates behaviour. We will: 1) Use phosphoproteome and kinome analysis to describe OPN3 intracellular signalling pathways in the SON; 2) Map the neuronal pathways of OPN3 MCNs; 3) Use light as a ligand to ask if OPN3 can modulate axonal and somato-dendritic release of AVP; 4) Use light as a ligand to ask if OPN3 can modulate MCN neuronal activity; 5) Determine whether blue light effects on sleep and wakefulness are mediated by SON OPN3; These studies will identify intra- and inter-cellular pathways that mediate the action of OPN3 and will define roles for OPN3 in secretion, neuronal activity and sleep/wakefulness. We will then link pathways to function. We will deliver mutant proteins into the SON carrying targeted phosphomimetic substitutions. We will ask about the effects of these substitutions on axonal and somato-dendritic release of AVP/OXT, MCN neuronal activity and sleep and wakefulness. By taking advantage of our expertise in uncovering the physiological role of ignored genes in a particularly tractable system, we propose to shine light on the role of OPN3 in regulating activity-secretion coupling in hypothalamic magnocellular neurones (MCNs). Further, this work will reveal novel mechanisms whereby light controls brain activity in the context of the physiological and behavioural rhythms required for good health. In the longer term there are implications for understanding and possibly addressing the negative consequences of the modern lifestyles and work patterns that disrupt these rhythms. (AU)