title: Myosin light chain kinase and Src control membrane dynamics in volume recovery from cell swelling.
abstract: The expansion of the plasma membrane, which occurs during osmotic swelling of epithelia, must be retrieved for volume recovery, but the mechanisms are unknown. Here we have identified myosin light chain kinase (MLCK) as a regulator of membrane internalization in response to osmotic swelling in a model liver cell line. On hypotonic exposure, we found that there was time-dependent phosphorylation of the MLCK substrate myosin II regulatory light chain. At the sides of the cell, MLCK and myosin II localized to swelling-induced membrane blebs with actin just before retraction, and MLCK inhibition led to persistent blebbing and attenuated cell volume recovery. At the base of the cell, MLCK also localized to dynamic actin-coated rings and patches upon swelling, which were associated with uptake of the membrane marker FM4-64X, consistent with sites of membrane internalization. Hypotonic exposure evoked increased biochemical association of the cell volume regulator Src with MLCK and with the endocytosis regulators cortactin and dynamin, which colocalized within these structures. Inhibition of either Src or MLCK led to altered patch and ring lifetimes, consistent with the concept that Src and MLCK form a swelling-induced protein complex that regulates volume recovery through membrane turnover and compensatory endocytosis under osmotic stress.
authors.affiliation: Department of Pharmacology, University of Vermont, Burlington, VT 05405 Department of Medicine, University of Vermont, Burlington, VT 05405, USA.
authors.forename: Elisabeth T
authors.initials: ET
authors.lastname: Barfod
authors.forename: Ann L
authors.initials: AL
authors.lastname: Moore
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Van de Graaf
authors.forename: Steven D
authors.initials: SD
authors.lastname: Lidofsky
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D024722:Cardiac Myosins / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D048429:Cell Size; D022081:Cell Surface Extensions / Q000378:metabolism; D051356:Cortactin / Q000378:metabolism; D034281:Dynamins / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008954:Models, Biological; D018994:Myosin Light Chains / Q000378:metabolism; D024462:Myosin Type II / Q000378:metabolism; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism*; D009997:Osmotic Pressure; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D000199:Actins; D051356:Cortactin; D018994:Myosin Light Chains; D011993:Recombinant Fusion Proteins; C107184:myosin light chain 2; D049452:Green Fluorescent Proteins; D019000:Phosphotyrosine; D019061:src-Family Kinases; D009219:Myosin-Light-Chain Kinase; D024722:Cardiac Myosins; D024462:Myosin Type II; D034281:Dynamins