NECAB1 and NECAB2 are Prevalent Calcium-Binding Proteins of CB1/CCK-Positive GABAergic Interneurons

• Published in: Cerebral cortex (New York, N.Y. 1991) N.Y. 1991), 2021-02, Vol.31 (3), p.1786-1806
• Main Authors: Miczán, Vivien, Kelemen, Krisztina, Glavinics, Judit R, László, Zsófia I, Barti, Benjámin, Kenesei, Kata, Kisfali, Máté, Katona, István
• Format: Article
• Language: English
• Subjects: Animals; Brain - metabolism; Calcium-Binding Proteins - metabolism; Cholecystokinin - metabolism; Eye Proteins - metabolism; GABAergic Neurons - metabolism; Interneurons - metabolism; Male; Mice; Mice, Inbred C57BL; Original; Receptor, Cannabinoid, CB1 - metabolism
• ISSN: 1047-3211; 1460-2199
• DOI: 10.1093/cercor/bhaa326

Abstract The molecular repertoire of the “Ca2+-signaling toolkit” supports the specific kinetic requirements of Ca2+-dependent processes in different neuronal types. A well-known example is the unique expression pattern of calcium-binding proteins, such as parvalbumin, calbindin, and calretinin. These cytosolic Ca2+-buffers control presynaptic and somatodendritic processes in a cell-type-specific manner and have been used as neurochemical markers of GABAergic interneuron types for decades. Surprisingly, to date no typifying calcium-binding proteins have been found in CB1 cannabinoid receptor/cholecystokinin (CB1/CCK)-positive interneurons that represent a large population of GABAergic cells in cortical circuits. Because CB1/CCK-positive interneurons display disparate presynaptic and somatodendritic Ca2+-transients compared with other interneurons, we tested the hypothesis that they express alternative calcium-binding proteins. By in silico data mining in mouse single-cell RNA-seq databases, we identified high expression of Necab1 and Necab2 genes encoding N-terminal EF-hand calcium-binding proteins 1 and 2, respectively, in CB1/CCK-positive interneurons. Fluorescent in situ hybridization and immunostaining revealed cell-type-specific distribution of NECAB1 and NECAB2 throughout the isocortex, hippocampal formation, and basolateral amygdala complex. Combination of patch-clamp electrophysiology, confocal, and STORM super-resolution microscopy uncovered subcellular nanoscale differences indicating functional division of labor between the two calcium-binding proteins. These findings highlight NECAB1 and NECAB2 as predominant calcium-binding proteins in CB1/CCK-positive interneurons.