title: Membrane properties involved in calcium-stimulated microparticle release from the plasma membranes of S49 lymphoma cells.
abstract: This study answered the question of whether biophysical mechanisms for microparticle shedding discovered in platelets and erythrocytes also apply to nucleated cells: cytoskeletal disruption, potassium efflux, transbilayer phospholipid migration, and membrane disordering. The calcium ionophore, ionomycin, disrupted the actin cytoskeleton of S49 lymphoma cells and produced rapid release of microparticles. This release was significantly inhibited by interventions that impaired calcium-activated potassium current. Microparticle release was also greatly reduced in a lymphocyte cell line deficient in the expression of scramblase, the enzyme responsible for calcium-stimulated dismantling of the normal phospholipid transbilayer asymmetry. Rescue of the scrambling function at high ionophore concentration also resulted in enhanced particle shedding. The effect of membrane physical properties was addressed by varying the experimental temperature (32-42°C). A significant positive trend in the rate of microparticle release as a function of temperature was observed. Fluorescence experiments with trimethylammonium diphenylhexatriene and Patman revealed significant decrease in the level of apparent membrane order along that temperature range. These results demonstrated that biophysical mechanisms involved in microparticle release from platelets and erythrocytes apply also to lymphocytes.
authors.affiliation: Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84601, USA.
authors.forename: Lauryl E
authors.initials: LE
authors.lastname: Campbell
authors.affiliation: Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84601, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Nelson
authors.affiliation: Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84601, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Gibbons
authors.affiliation: Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84601, USA.
authors.forename: Allan M
authors.initials: AM
authors.lastname: Judd
authors.affiliation: Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84601, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Bell
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D061207:Calcium Ionophores / Q000494:pharmacology; D020013:Calcium Signaling; D045744:Cell Line, Tumor; D055252:Cell-Derived Microparticles / Q000378:metabolism* / Q000473:pathology; D015759:Ionomycin / Q000494:pharmacology; D008223:Lymphoma / Q000378:metabolism* / Q000473:pathology; D051379:Mice
chemical_list: D061207:Calcium Ionophores; D015759:Ionomycin; D002118:Calcium