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LRRC8A-containing chloride channel is crucial for cell volume recovery and survival under hypertonic conditions

ABSTRACT: Regulation of cell volume is essential for tissue homeostasis and cell viability. In response to hypertonic stress, cells need rapid electrolyte influx to compensate water loss and to prevent cell death in a process known as regulatory volume increase (RVI). However, the molecular component able to trigger such process was unknown to date. Using a genome wide CRISPR/Cas9 screen, we identified LRRC8A, which encodes a chloride channel subunit, as the gene most associated with cell survival under hypertonic conditions. Hypertonicity activates the p38 stress-activated protein kinase pathway and its downstream MSK1 kinase, which phosphorylates and activates LRRC8A. LRRC8A-mediated Cl efflux facilitates activation of the with-no-lysine (WNK) kinase pathway, which in turn, promotes electrolyte influx via Na+ /K+ /2Cl cotransporter (NKCC) and RVI under hypertonic stress. LRRC8A-S217A mutation impairs channel activation by MSK1, resulting in reduced RVI and cell survival. In summary, LRRC8A is key to bidirectional osmotic stress responses and cell survival under hypertonic conditions.

ORGANISM(S): Homo sapiens

PROVIDER: GSE158316 | GEO | 2021/05/29

REPOSITORIES: GEO

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Project description:Protein function is controlled by the cellular proteostasis network. Proteostasis is energetically costly and those costs must be balanced with the energy needs of other physiological functions. Hypertonic stress causes widespread protein damage in C. elegans. Suppression and management of protein damage is essential for optimal survival under hypertonic conditions. ASH chemosensory neurons allow C. elegans to detect and avoid strongly hypertonic environments. We demonstrate that gene mutations that disrupt ASH mediated hypertonic avoidance behavior or genetic ablation of ASH neurons enhance survival during hypertonic stress. Enhanced survival is not due to altered systemic volume homeostasis or organic osmolyte accumulation. Instead, loss of ASH neuron function reduces protein damage in non-neuronal cells. Improved proteostasis capacity is due in part to upregulation of genes that play important roles in managing protein damage. We propose that inhibitory signaling from ASH neurons normally suppresses expression of genes required for non-neuronal cell proteostasis. Because all cells have the capacity to sense and respond to stressors, inhibitory neuronal signaling may be important for minimizing activation of cellular stress resistance and proteostasis pathways during short duration and less extreme stressors or stressors that can be avoided by behavioral changes. Neuronal regulation of systemic proteostasis allows the nervous system to monitor environmental variables and more effectively partition finite energy resources between different organismal processes. Our studies add to a growing body of work demonstrating that intercellular communication between neuronal and non-neuronal cells plays a critical role in integrating cellular stress resistance with other organismal physiological demands and associated energy costs. mRNA expression profiling of synchronized L4 stage wild-type N2 Bristol and VC1262 osm-9(ok1677) C. elegans strains under control (51mM NaCl) and hypertonic stress (200mM NaCl).

Project description:Analysis of alterations in the hippocampus transcriptome caused by deletion of Mitogen Stress activated Kinase 1 (MSK1). MAPK signaling has been implicated in a wide range of neuronal processes, including development, plasticity and viability. One of the principal downstream targets of both the ERK/MAPK pathway and the p38 MAPK pathway is Mitogen Stress activated Kinase 1 (MSK1). Here, we sought to understand the role that MSK1 plays in neuroprotection against excitotoxic stimulation in the hippocampus. To this end, we utilized a MSK1 null mouse line, cell viability assays and array-based profiling approaches. Here we show that MSK1 is broadly expressed within the major neuronal cell layers of the hippocampus and that status epilepticus (SE) drives acute induction of MSK1 activation. In response to the SE paradigm, MSK1 KO mice exhibited a striking increase in vulnerability to pilocarpine-evoked cell death within the CA1 and CA3 cell layers. Further, cultured MSK1 null neurons exhibited a heighted level of NMDA-evoked excitotoxicity relative to WT neurons, as assessed using the LDH assay. Given these findings, we examined the hippocampal transcriptional profile of MSK1 null mice. Affymetrix array profiling revealed that with MSK1 deletion a total of 115 genes showed significant changes (> 1.25-fold) in expression. Notably, functional analysis indicated that a subset of these genes contribute to neuroprotective signaling networks. Together, these data provide important new insights into the mechanism by which the MAPK/MSK1 signaling cassette confers neuroprotection against excitotoxic insults. Approaches designed to upregulate or mimic the functional effects of MSK1 may prove beneficial against an array of degenerative processes resulting from excitotoxic insults. MAPK signaling has been implicated in a wide range of neuronal processes, including development, plasticity and viability. One of the principal downstream targets of both the ERK/MAPK pathway and the p38 MAPK pathway is Mitogen Stress activated Kinase 1 (MSK1). Here, we sought to understand the role that MSK1 plays in neuroprotection against excitotoxic stimulation in the hippocampus. To this end, we utilized a MSK1 null mouse line, cell viability assays and array-based profiling approaches. Here we show that MSK1 is broadly expressed within the major neuronal cell layers of the hippocampus and that status epilepticus (SE) drives acute induction of MSK1 activation. In response to the SE paradigm, MSK1 KO mice exhibited a striking increase in vulnerability to pilocarpine-evoked cell death within the CA1 and CA3 cell layers. Further, cultured MSK1 null neurons exhibited a heighted level of NMDA-evoked excitotoxicity relative to WT neurons, as assessed using the LDH assay. Given these findings, we examined the hippocampal transcriptional profile of MSK1 null mice. Affymetrix array profiling revealed that with MSK1 deletion a total of 115 genes showed significant changes (> 1.25-fold) in expression. Notably, functional analysis indicated that a subset of these genes contribute to neuroprotective signaling networks. Together, these data provide important new insights into the mechanism by which the MAPK/MSK1 signaling cassette confers neuroprotection against excitotoxic insults. Approaches designed to upregulate or mimic the functional effects of MSK1 may prove beneficial against an array of degenerative processes resulting from excitotoxic insults.

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LRRC8A-containing chloride channel is crucial for cell volume recovery and survival under hypertonic conditions

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