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Mice deficient in the NAAG synthetase II gene Rimkla are impaired in a novel object recognition task
Author(s) -
Becker Ivonne,
WangEckhardt Lihua,
LodderGadaczek Julia,
Wang Yong,
Grünewald Agathe,
Eckhardt Matthias
Publication year - 2021
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/jnc.15333
Subject(s) - glutamate carboxypeptidase ii , parvalbumin , neuroscience , neuropeptide , glutamate receptor , gabaergic , endocrinology , biology , brainstem , recognition memory , neurotransmitter , medicine , central nervous system , psychology , biochemistry , cognition , genetics , inhibitory postsynaptic potential , receptor , cancer , prostate
Abstract N‐acetylaspartylglutamate (NAAG) is an abundant neuropeptide in the mammalian nervous system, synthesized by two related NAAG synthetases I and II (NAAGS‐I and ‐II) encoded by the genes Rimklb and Rimkla, respectively. NAAG plays a role in cognition and memory, according to studies using inhibitors of the NAAG hydrolase glutamate carboxypeptidase II that increase NAAG concentration. To examine consequences of reduced NAAG concentration, Rimkla‐deficient (Rimkla −/− ) mice were generated. These mice exhibit normal NAAG level at birth, likely because of the intact Rimklb gene, but have significantly reduced NAAG levels in all brain regions in adulthood. In wild type mice NAAGS‐II was most abundant in brainstem and spinal cord, as demonstrated using a new NAAGS‐II antiserum. In the hippocampus, NAAGS‐II was only detectable in neurons expressing parvalbumin, a marker of GABAergic interneurons. Apart from reduced open field activity, general behavior of adult (6 months old) Rimkla −/− mice examined in different tests (dark‐light transition, optokinetic behavior, rotarod, and alternating T‐maze) was not significantly altered. However, Rimkla −/− mice were impaired in a short‐term novel object recognition test. This was also the case for mice lacking NAA synthase Nat8l, which are devoid of NAAG. Together with results from previous studies showing that inhibition of the NAAG degrading enzyme glutamate carboxypeptidase II is associated with a significant improvement in object recognition, these results suggest a direct involvement of NAAG synthesized by NAAGS‐II in the memory consolidation underlying the novel object recognition task.