Plasma Membrane Sorting of Muscarinic Acetylcholine Receptors

Abstract

Cellular polarization is a process whereby a cell's structure and components are organized asymmetrically. Proper polarization is essential for cellular function in many different cell types. Immunocytochemical studies have shown that muscarinic acetylcholine receptors are sorted into different plasma membrane domains depending on the cell type and receptor subtype. In this study, we use immunocytochemistry to determine the plasma membrane sorting of the M1 and M2 muscarinic receptor in cultured cortical neurons. Using MAP2 and Tau1 as somatodendritic and axonal markers, respectively, we determined that sufficient polarization of neurons cultured in vitro occurs within 5-8 days after initial culturing. The sorting of the M1 and M2 receptors in cortical neurons remains inconclusive. We also explored the effects of muscarinic receptor dimerization on the plasma membrane sorting of the M1 and M2 receptors in the Madin-Darby Canine Kidney epithelial cell line. Transfection of an epitope tagged M1 receptor showed mostly basolateral sorting in MDCK cells. The plasma membrane sorting of an M1-M2 receptor dimer remains inconclusive.