LAUSR

HIGHLIGHTSSRM‐MS method for the identification and differentiation of CB1 and CB1b.Application of the method to CHO cells transduced with CB1 or CB1b. ABSTRACT Cannabinoid receptors (CBR), including CB1 and CB2 have been therapeutic targets for a number of conditions. Recently, splice variants of the CB1R have been identified in humans. The isoforms differ in their N‐terminus sequence and pharmacological activity relative to the CB1R, as a result, the differentiation between the CB1 receptor and its isoform is required. As a result, a selected reaction monitoring mass spectrometry (SRM‐MS) method was developed for the quantitation of CB1 and the CB1b isoform in CHO cells transduced with CB1 and CB1b. The SRM‐MS protocol was assessed with isotopically labeled peptide standards and had high reproducibility of intra‐day assay (CVs from 1.9 to 4.3% for CB1 and 0.5 to 5.9% for CB1b) and inter‐day assay (CVs from 1.2 to 5.2% for CB1 and 1.2 to 6.1% for CB1b).