Caenorhabditis Elegans AMsh Glia Sense Repulsive Odors Via GPCR Pathways

Glial cell and neuron are two important components of nervous system,neurons are applicable to sense,transmit,process and feedback informations,while glial cells are function in support,insulation,nutrition and protect neurons.People seen glial cell as a kind of supportive and negative cells in nervous system.At the beginning of 1990s,researchers found that Ca2+ fluctuations were existed in astrocytes,and the astrocytic Ca2+ fluctuations strating in one astrocyte could induce Ca2+ fluctuation in adjacent astrocytes,developed a local "calcium wave" spreading,which is similar to neuronal information propagation.These phenomenons were also checked existing in mice brain in vivo.Scientists believed that glial cells also have "active" state and "inactive" state,"calcium wave" was a way of information propagation between glial cells.As an important model organism,Caenorhabditis elegans(C.elegans)have complete nervous system and complex physiological functions.Amphid sheath glial cell(AMsh glia)in head connect with many sensory neuronal receptive endings(NREs),play an important role in maintenance the normal neuronal functions.In this study,we found that high isoamyl alcohol(IAA)induced remarkable Ca2+ elevation in AMsh glia,which is similar to the activation of ASH sensory neuron,but the rate of Ca2+ elevation in AMsh glia was lower than in ASH neuron.Furthermore,different times and concentrations of IAA application induced different types of AMsh glia Ca2+ elevation,sustain and return.Next,we found that only repulsive odors could induce AMsh glia Ca2+ elevation,whereas neither different concentrations of attractive odors nor non-odor repellents induce AMsh glia Ca2+ elevation,suggesting that only repulsive odors could activate AMsh glia.According to the unique AMsh glia response spectrum,we suspected that AMsh glia have the ability of sensing repulsive odors independently.Then we used both Capsaicin-TRPV1 system and histamine-HisCll system to activate/suppress neuronal activation,we found that neuronal activation couldn’t induce any of AMsh glia Ca2+ elevation,and neuronal suppression couldn’t inhibit any of AMsh glia Ca2+ elevation,these results confirmed that AMsh glia was a repulsive odor sensor.Based on serials of mutation and rescue assays,we found that CNG channel TAX-2,TRPV channel OSM-9,Ga protein GPA-3 directly act in the process of AMsh glia Ca2+ elevation.High-IAA induced Ca2+ elevation was arised from endoplasmic reticulum calcium store release mediated by IP3R/ITR-1 channel,and TAX-2/OSM-9 channel induced Ca2+ influx.We then checked the mRNA transcripts of tax-2,osm-9,gpa-3 and itr-1 genes through single cell RT-PCR,all of these transcripts were existed in AMsh glia.Our work firstly found that C.elegans AMsh glia could independtly sense repulsive odors,preliminarily clarified the function of some important proteins involved in this process,these new discovery brought some references and bases for further investigating the role of glial cells in the future.