Interactions of TRPC-ion channels with membrane lipids

TRPC (transient receptor potential, canonical type) proteins represent examples of ionic channels that reside in specialized microdomains of the plasma membrane, termed lipid rafts. Lipid composition and topology in raft domains is considered essential for proper function of raft-resident signaling molecules. Membrane lipids may interact with distinct protein structures and govern protein targeting and recruitment as well as membrane shape and fluidity, and, as a consequence, the function of membrane-associated signalplexes. The molecular mechanisms by which membrane lipids control signalling events such as the gating of raft-resident ion channel proteins, is still elusive. This project is proposed with the aim to elucidate the interactions between membrane lipids and the raft-resident TRPC channel proteins TRPC3, TRPC4 and TRPC6. We will focus on lipid regulation of assembly and gating of TRPC channel complexes, and analyze the underlying molecular mechanisms. The main questions that will be addressed are: i) How does the membrane lipid composition affect TRPC channel function, and which lipids are of particular regulatory impact? ii) Are TRPC proteins able to sense specific lipids such as sterols or phospholipids in terms of direct, regulatory protein-lipid interations? iii) Do membrane lipids interfere with the ability of TRPC proteins to interact with signaling partners in membrane microdomains? iv) Do membrane lipids interfere with assembly of TRPC proteins in terms of the formation of functional homo- or heterotetramers? v) Do membrane lipids interfere with protein transport related mechanisms including vesicle-fusion mediated membrane insertion of TRPC proteins? These questions will be addressed by an approach that combines classical methods for measurement of ion channel function such as patch clamp experiments and intracellular ion measurements as well as novel approaches for detection of protein-lipid interaction as well as high resolution fluorescence microscopy (FRET-, TIRF- and single molecule microscopy). These methods will be deployed in experiments utilizing the HEK293 expression system as well as in cell systems that display expression of native, raft-resident TRPC species (vascular smooth muscle cells). The proposed investigations on the regulatory impact of membrane lipids on TRPC cation channels is expected to discover novel principles of regulatory lipid-protein interactions and widen the scope to develop therapeutic strategies that target raft-resident signaling pathways.

TRPC (transient receptor potential, canonical type) proteins represent examples of ionic channels that reside in specialized microdomains of the plasma membrane, termed lipid rafts. Lipid composition and topology in raft domains is considered essential for proper function of raft-resident signaling molecules. Membrane lipids may interact with distinct protein structures and govern protein targeting and recruitment as well as membrane shape and fluidity, and, as a consequence, the function of membrane-associated signalplexes. The molecular mechanisms by which membrane lipids control signalling events such as the gating of raft-resident ion channel proteins, is still elusive. This project is proposed with the aim to elucidate the interactions between membrane lipids and the raft- resident TRPC channel proteins TRPC3, TRPC4 and TRPC6. We will focus on lipid regulation of assembly and gating of TRPC channel complexes, and analyze the underlying molecular mechanisms. The main questions that will be addressed are: 1. How does the membrane lipid composition affect TRPC channel function, and which lipids are of particular regulatory impact? 2. Are TRPC proteins able to sense specific lipids such as sterols or phospholipids in terms of direct, regulatory protein-lipid interations? 3. Do membrane lipids interfere with the ability of TRPC proteins to interact with signaling partners in membrane microdomains? 4. Do membrane lipids interfere with assembly of TRPC proteins in terms of the formation of functional homo- or heterotetramers? 5. Do membrane lipids interfere with protein transport related mechanisms including vesicle-fusion mediated membrane insertion of TRPC proteins? These questions will be addressed by an approach that combines classical methods for measurement of ion channel function such as patch clamp experiments and intracellular ion measurements as well as novel approaches for detection of protein-lipid interaction as well as high resolution fluorescence microscopy (FRET-, TIRF- and single molecule microscopy). These methods will be deployed in experiments utilizing the HEK293 expression system as well as in cell systems that display expression of native, raft-resident TRPC species (vascular smooth muscle cells). The proposed investigations on the regulatory impact of membrane lipids on TRPC cation channels is expected to discover novel principles of regulatory lipid-protein interactions and widen the scope to develop therapeutic strategies that target raft-resident signaling pathways.