Secretory pathway pumps
The interest of the group is to understand the mechanisms underlying lipid translocation across biological membranes and vesicle formation along the secretory pathway. Our recent data suggests that these two processes are connected by the action of a family of protein pumps known as P4-ATPases (also called flippases). We currently focus on two parallel research interests: 1) How do P4-ATPases translocate lipids across membranes?; 2) How is lipid translocation regulated in living cells? To unravel these questions we use a broad range of techniques. This include: transient expression in tobacco epidermal cells, bioimaging, molecular cloning and mutant generation and characterization, analysis of protein-protein interactions, and purification of membrane proteins expressed in heterologous systems.
Selected figures from our publication in Plant Cell (2008) showing different aspects in which the flippase group is interested. From left to right: i) GUS-staining of an Arabidopsis root tip showing expression of the flippase ALA3; ii) electron-micrograph of Arabidopsis root cells specialized in secretion; iii) tobacco epidermal leaf cell expressing YFP-tagged ALA3; iv) proposed mechanism of action of flippases in lipid translocation.
The Arabidopsis flippase ALA2 localizes to the prevacuolar compartment. Right panel, fluorescence of ALA2 tagged with Green Fluorescent Protein (GFP). Middle panel, fluorescence of an endoplasmatic reticulum protein marker tagged with Yellow Fluorescent Protein (YFP). Left, overlay of both fluorescent images.
López-Marqués RL, Holthuis JC, Pomorski TG (2011) Pumping lipids with P4-ATPases. Biol Chem. 392(1-2):67-76.
López-Marqués RL, Poulsen RL, Hanisch S, Meffert K, Buch-Pedersen MJ, Jakobsen MK, Pomorski TG and Palmgren MG (2010) Intracellular targeting signals and lipid specificity determinants of the ALA/ALIS P4-ATPase complex reside in the catalytic ALA α-subunit. Mol. Biol. Cell 21, 791-801.
Poulsen L, López-Marqués RL, Schulz A, MacDowell S, Okkeri J, Licht D, Pomorski T, Harper JF and Palmgren MG, The Arabidopsis P4-ATPase ALA3 localizes to the golgi and requires a beta-subunit to function in lipid translocation and secretory vesicle formation. Plant Cell 20 (2008), 658-676.
Poulsen LR, López-Marques RL and Palmgren MG, Flippases: still more questions than answers, Cell. Mol. Life Sci. 65 (2008), 3119-3125.