title: Plasticity of the asialoglycoprotein receptor deciphered by ensemble FRET imaging and single-molecule counting PALM imaging.
abstract: The stoichiometry and composition of membrane protein receptors are critical to their function. However, the inability to assess receptor subunit stoichiometry in situ has hampered efforts to relate receptor structures to functional states. Here, we address this problem for the asialoglycoprotein receptor using ensemble FRET imaging, analytical modeling, and single-molecule counting with photoactivated localization microscopy (PALM). We show that the two subunits of asialoglycoprotein receptor [rat hepatic lectin 1 (RHL1) and RHL2] can assemble into both homo- and hetero-oligomeric complexes, displaying three forms with distinct ligand specificities that coexist on the plasma membrane: higher-order homo-oligomers of RHL1, higher-order hetero-oligomers of RHL1 and RHL2 with two-to-one stoichiometry, and the homo-dimer RHL2 with little tendency to further homo-oligomerize. Levels of these complexes can be modulated in the plasma membrane by exogenous ligands. Thus, even a simple two-subunit receptor can exhibit remarkable plasticity in structure, and consequently function, underscoring the importance of deciphering oligomerization in single cells at the single-molecule level.
authors.affiliation: Section on Organelle Biology and Unit on Cellular Polarity, The Eunice Kennedy Shriver National Institute of Child Health and Human Development, Cell Biology and Metabolism Branch, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Malte
authors.initials: M
authors.lastname: Renz
authors.forename: Brian R
authors.initials: BR
authors.lastname: Daniels
authors.forename: György
authors.initials: G
authors.lastname: Vámosi
authors.forename: Irwin M
authors.initials: IM
authors.lastname: Arias
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lippincott-Schwartz
mesh_terms: D037263:Asialoglycoprotein Receptor / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D008024:Ligands; D018613:Microscopy, Confocal / Q000379:methods*
chemical_list: D037263:Asialoglycoprotein Receptor; D008024:Ligands