CLIC1 null mice demonstrate a role for CLIC1 in macrophage superoxide production and tissue injury

Abstract

We generated and studied CLIC1 null (C1KO) mice to investigate the physiological role of this protein. C1KO and matched wild‐type (WT) mice were studied in two models of acute toxic tissue injury. CLIC1 expression is upregulated following acute injury of WT kidney and pancreas and is absent in C1KOs. Acute tissue injury is attenuated in the C1KOs and this correlates with an absence of the rise in tissue reactive oxygen species (ROS) that is seen in WT mice. Infiltration of injured tissue by inflammatory cells was comparable between WT and C1KOs. Absence of CLIC1 increased PMA‐induced superoxide production by isolated peritoneal neutrophils but dramatically decreased PMA‐induced superoxide production by peritoneal macrophages. CLIC1 is expressed in both neutrophils and macrophages in a peripheral pattern consistent with either plasma membrane or the cortical cytoskeleton in resting cells and redistributes away from the periphery following PMA stimulation in both cell types. Absence of CLIC1 had no effect on redistribution or dephosphorylation of Ezrin/ERM cytoskeleton in macrophages. Plasma membrane chloride conductance is altered in the absence of CLIC1, but not in a way that would be expected to block superoxide production. NADPH oxidase redistributes from an intracellular compartment to the plasma membrane when WT macrophages are stimulated to produce superoxide and this redistribution fails to occur in C1KO macrophages. We conclude that the role of CLIC1 in macrophage superoxide production is to support redistribution of NADPH oxidase to the plasma membrane, and not through major effects on ERM cytoskeleton or by acting as a plasma membrane chloride channel.

Three Decades of Chloride Intracellular Channel Proteins: From Organelle to Organ Physiology

“…CLIC1 affects the innate arm of the immune system. It is highly expressed in macrophages and modulates the phagosomal proteolytic activity of macrophages via ROS generation (Jiang et al., ; Ulmasov et al., ). Furthermore, upon interaction with heat‐inactivated Candida albicans cells, RAW 264.7 macrophages show a decrease in expression of CLIC1 (Martinez‐Solano, Reales‐Calderon, Nombela, Molero, & Gil, ) as well as suppressed TNF‐α levels.…”

“…CLICs belong to the family of intracellular ion channels that includes the mitochondrial large‐conductance Ca 2+ ‐activated K + channel (mitoBK Ca ), mitochondrial ATP‐dependent K + channel (mitoK ATP ), voltage‐dependent anion channel (VDAC), mitochondrial calcium uniporter (MCU), ryanodine receptor (RyR), and inositol triphosphate receptor (IP3R; Kiselyov & Muallem, ; Leanza et al., ; O'Rourke, ; Singh et al., ). There are six mammalian CLIC paralogs and, under physiological conditions, the majority of the CLICs are present on intracellular organelles and in the cytoplasm (Singh, ; Ulmasov et al., ). In addition to intracellular organelle membranes, CLICs can associate with the plasma membrane (Averaimo, Milton, Duchen, & Mazzanti, ; Milton et al., ; Tang et al., ; Warton et al., ) under pathological conditions or upon overexpression.…”

Chloride intracellular channel 1 cooperates with potassium channel EAG2 to promote medulloblastoma growth

“…Given its presence as a soluble protein in the cytosol, phylogenetic prediction suggests that CLIC1 may have enzymatic function ( Littler et al, 2010 ), and soluble CLIC1 displays glutathione-dependent oxidoreductase activity in a cell-free system ( Al Khamici et al, 2015 ). Clic1 knockout mice were viable and fertile and appeared normal, aside from showing a mild defect in platelets and macrophages ( Qiu et al, 2010 ; Ulmasov et al, 2017 ).…”

CLIC1 Protein Accumulates in Circulating Monocyte Membrane during Neurodegeneration

“…It is an active element that contributes to the condition of oxidative stress in the cell [12][13][14], has functional connection with the cytoskeleton [15][16][17], and once in the membrane, it controls chloride flux through the lipid bilayer [10,11,19]. All these functions are linked to cell proliferation, cell migration and infiltration [11,13,[15][16][17]19]. We focused on monocytes because they are the ideal elements to investigate CLIC1 properties.…”

“…Once in the transmembrane form, CLIC1 is associated with chloride ions' permeability [10,11]. Recent investigation demonstrated that tmCLIC1 and NADPH oxidase are involved in a feed-forward mechanism that increases the production of reactive oxygen species (ROS) [12], particularly in macrophages [13]. This is instrumental in speeding up the transition G1/S phase during the cell cycle [14].…”