REM sleep is unique to animals with highly advanced brain structures. Molecular/cellular mechanisms of REM sleep regulation remain largely unknown. The Dreamless mutant mice with a single amino acid substitution (N315K) in the NALCN protein show abnormalities in the homeostasis of REM sleep (Funato et al, Nature, 2016). NALCN is a voltage-independent cation channel known to be involved in the circadian rhythm and respiratory regulation. However, the components of NALCN channel complex and molecular mechanisms of NALCN regulation in REM sleep homeostasis are unclear. We are trying to comprehensively search for unknown protein-protein interactions of NALCN by using the biotin-based proximity labeling technique, BioID. Recently, the MAC-tag (consisting of HA-tag, strepIII-tag, and promiscuous mutant biotin ligase BirA^*) was developed, that enables parallel analyses of both BioID and conventional affinity purified mass spectrometry (AP-MS). In this study, we generated several lines of knock-in mice, in which a MAC-tag was fused to NALCN, UNC80, or NLF-1, currently known components of the NALCN channel complex. We confirmed no expression changes in the target alleles at the mRNA and protein levels. Using these mice, we identified several interacting proteins of each target by AP-MS. In the future, we will perform comprehensive mapping of NALCN protein interactions by proteomic analyses through BioID, in order to identify novel proteins involved in the molecular regulation of NALCN that are relevant for REM sleep homeostasis.