The cysteine-rich with EGF-Like domains 2 (CRELD2) protein interacts with the large cytoplasmic domain of human neuronal nicotinic acetylcholine receptor α4 and β2 subunits

Abstract

Using a yeast two-hybrid screening we report the isolation of a novel human protein, hCRELD2β, that interacts specifically with the large cytoplasmic regions of human nicotinic acetylcholine receptor (nAChR) α4 and β2 subunits, both in yeast cells and in vitro. This interaction is not detected with nAChR α7 and α3 subunits. The hCRELD2 gene encodes for multiple transcripts, likely to produce multiple protein isoforms. A previously reported one has been renamed as CRELD2α. Isoforms α and β are expressed in all tissues examined and have the same N-terminal and central regions but alternative C-terminal regions. Both isoforms interact with the α4 subunit. Within this subunit the interaction was localized to the N-terminal region of the large cytoplasmic loop. The CRELD2β protein is present at the endoplasmic reticulum where colocalized with α4β2 nAChRs upon cell transfection. Immunohistochemistry experiments demonstrated the presence of CRELD2 in the rat brain at sites where α4β2 receptors have been previously detected. Labeling was restricted to neuronal perikarya. Finally, CRELD2 decreases the functional expression and impairs membrane transport of α4β2 nAChRs in Xenopus leavis oocytes, without affecting α3β4 and α7 nAChR expression. These results suggest that CRELD2 can act as a specific regulatorof α4β2 nAChR expression. © 2005 International Society for Neurochemistry.