Chacterization of Paramecium Tetraurelia Ciliary Membrane Plasma Membrane Calcium Pumps and Lipid Rafts

• Main Author: Ray, Koela
• Format: Others
• Published: ScholarWorks @ UVM 2008
• Subjects: paramecium; lipid rafts
• Online Access: http://scholarworks.uvm.edu/graddis/190; http://scholarworks.uvm.edu/cgi/viewcontent.cgi?article=1189&context=graddis

Paramecium, a ciliate, is an important model for studying Ca2+ signaling and understanding chemoreception and signal transduction. There are several proteins, such as plasma membrane calcium ATPases (PMCAs)/ calcium pumps, SERCA pumps, calmodulin and Ca2+ channels that play an important role in maintaining intracellular Ca2+ level and signaling in Paramecium. Isoform 2 of PMCA has been identified in both the cilia and pellicle membranes of Paramecium, the activity of which leads to hyperpolarization. Plasma and ciliary membrane of Paramecium is made up of a variety of sterols and sphingolipids which constitute lipid rafts, demonstrated by the presence of detergent resistant membranes and their distribution in sucrose and Optiprep density gradients. PMCAs are important markers of lipid rafts and PMCA 2 is found to be localized in lipid rafts of both the cilia and somatic membrane of Paramecium. Methyl-β-cyclodextrin treatment can remove up to 42% of sterols from pellicle membranes but only about 12% from cilia. Sterol depletion of pellicle perturbs the distribution of PMCA 2 and other raft proteins in pellicle which is not observed in cilia as evident from western blot analysis and immunomicroscopic studies. There is evidence that selection of gradient medium for study of lipid rafts and its associated proteins is very important in Paramecium. Glutamate receptors and adenylyl cyclase, the upstream molecules of the signal transduction pathway through PMCA have also been identified in cellular cilia, indicating that these raft molecules forms a platform for signaling in Paramecium cilia.