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Báo cáo khoa học: Functional reconstitution of mammalian ‘chloride intracellular channels’ CLIC1, CLIC4 and CLIC5 reveals differential regulation by cytoskeletal actin

Chloride intracellular channels (CLICs) are soluble, signal peptide-less pro-teins that are distantly related to W-type glutathione-S-transferases. Although some CLICs bypass the classical secretory pathway and auto-insert into cell membranes to form ion channels, their cellular roles remain unclear. | ễFEBS Journal Functional reconstitution of mammalian chloride intracellular channels CLIC1 CLIC4 and CLIC5 reveals differential regulation by cytoskeletal actin H. Singh M. A. Cousin and R. H. Ashley Centre for Integrative Physiology University of Edinburgh MedicalSchool UK Keywords chloride intracellular channels cytoskeleton ion channel multiconductance channel planar bilayer Correspondence H. Singh Department of Physiology UCLA David Geffen Schoolof Medicine 10833 LeConte Avenue 53-373 CHS Los Angeles CA 90095-1751 USA Fax 1 310 206 5661 Tel 1 310 825 7185 Email hsingh@mednet.ucla.edu Present address Department of Physiology David Geffen Schoolof Medicine UCLA CA USA Received 10 September 2007 revised 10 October 2007 accepted 16 October 2007 doi 10.1111 j.1742-4658.2007.06145.x Chloride intracellular channels CLICs are soluble signal peptide-less proteins that are distantly related to W-type glutathione-S-transferases. Although some CLICs bypass the classical secretory pathway and autoinsert into cell membranes to form ion channels their cellular roles remain unclear. Many CLICs are strongly associated with cytoskeletal proteins but the role of these associations is not known. In this study we incorporated purified recombinant mammalian CLIC1 CLIC4 and for the first time CLIC5 into planar lipid bilayers and tested the hypothesis that the channels are regulated by actin. CLIC5 formed multiconductance channels that were almost equally permeable to Na K and Cl- suggesting that the CLIC nomenclature may need to be revised. CLIC1 and CLIC5 but not CLIC4 were strongly and reversibly inhibited or inactivated by cytosolic F-actin in the absence of any other protein. This inhibition effect on channels could be reversed by using cytochalasin to disrupt the F-actin. We suggest that actin-regulated membrane CLICs could modify solute transport at key stages during cellular events such as apoptosis cell and organelle division and fusion cell-volume regulation and cell .