Hippocampal protein kinase D1 is necessary for DHPG-induced learning and memory impairments in rats

PLOS ONE, Nov 2019

Background Understanding molecular mechanisms underlying the induction of learning and memory impairments remains a challenge. Recent investigations have shown that the activation of group I mGluRs (mGluR1 and mGluR5) in cultured hippocampal neurons by application of (S)-3,5-Dihydroxyphenylglycine (DHPG) causes the regulated internalization of N-methyl-D-aspartate receptors (NMDARs), which subsequently activates protein kinase D1 (PKD1). Through phosphorylating the C-terminals of the NMDAR GluN2 subunits, PKD1 down-regulates the activity of remaining (non-internalized) surface NMDARs. The knockdown of PKD1 does not affect the DHPG-induced inhibition of AMPA receptor-mediated miniature excitatory post-synaptic currents (mEPSCs) but prevents the DHPG-induced inhibition of NMDAR-mediated mEPSCs in vitro. Thus, we investigated the in vivo effects of bilateral infusions of DHPG into the hippocampal CA1 area of rats in the Morris water maze (MWM) and the novel object discrimination (NOD) tests. Methods A total of 300 adult male Sprague Dawley rats (250–280 g) were used for behavioral tests. One hundred ninety four were used in MWM test and the other 106 rats in the NOD test. Following one week of habituation to the vivarium, rats were bilaterally implanted under deep anesthesia with cannulas aimed at the CA1 area of the hippocampus (CA1 coordinates in mm from Bregma: AP -3.14; lateral +/-2; DV -3.0). Through implanted cannulas artificial cerebrospinal fluid (ACSF), the group1 mGluR antagonist 6-Methyl-2-(phenylethynyl)pyridine (MPEP), the dynamin-dependent internalization inhibitor Dynasore, or the PKD1 inhibitor CID755673 were infused into the bilateral hippocampal CA1 areas (2 μL per side, over 5 min). The effects of these infusions and the effects of PKD1 knockdown were examined in MWM or NOD test. Results DHPG infusion increased the latency to reach the platform in the MWM test and reduced the preference for the novel object in the NOD task. We found that the DHPG effects were dose-dependent and could be maintained for up to 2 days. Notably, these effects could be prevented by pre-infusion of the group1 mGluR antagonist MPEP, the dynamin-dependent internalization inhibitor Dynasore, the PKD1 inhibitor CID755673, or by PKD1 knockdown in the hippocampal CA1 area. Conclusion Altogether, these findings provide direct evidence that PKD1-mediated signaling may play a critical role in the induction of learning and memory impairments by DHPG infusion into the hippocampal CA1 area.

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Hippocampal protein kinase D1 is necessary for DHPG-induced learning and memory impairments in rats

April Hippocampal protein kinase D1 is necessary for DHPG-induced learning and memory impairments in rats Wei Wang 0 1 Florian Duclot 1 Bradley R. Groveman 1 Nicole Carrier 1 Haifa Qiao 1 Xiao- Qian Fang 1 Hui Wang 1 Wenkuan Xin 1 Xing-Hong Jiang 1 Michael W. Salter 1 Xin- Sheng Ding 0 1 Mohamed Kabbaj 1 Xian-Min Yu 1 0 Department of Neurology, the First Affiliated Hospital of Nanjing Medical University , Nanjing , People's Republic of China, 2 BenQ Affiliated Hospital and Neurological Institute, Nanjing Medical University , Nanjing , People's Republic of China, 3 Department of Biomedical Sciences, Florida State University , Tallahassee , Florida, United States of America, 4 Department of Biomedical Sciences, University of Texas Rio Grande Valley School of Medicine, Edinburg, Texas, United States of America, 5 College of Pharmaceutical Sciences, Southwest University , Chongqing , People's Republic of China, 6 Department of Physiology and Neurobiology, Medical College of Soochow University , Suzhou , People's Republic of China, 7 Program in Neuroscience and Mental Health, Hospital for Sick Children, University of Toronto , Toronto, Ontario , Canada 1 Editor: Michal Hetman, University of Louisville , UNITED STATES - Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was supported by the NIH: R01 NS053567 to XMY, and National Natural Science Foundation of China: NSFC #30971022 to XD, NSFC #31271258 and #81771187 to XHJ. MWS is supported in part by CIHR grant MT12682 and holds a Canada Research Chair (Tier I) in Neuroplasticity and Pain, and is the Anne and Max Tanenbaum Chair in Molecular Medicine at the Background Understanding molecular mechanisms underlying the induction of learning and memory impairments remains a challenge. Recent investigations have shown that the activation of group I mGluRs (mGluR1 and mGluR5) in cultured hippocampal neurons by application of (S)-3,5-Dihydroxyphenylglycine (DHPG) causes the regulated internalization of N-methylD-aspartate receptors (NMDARs), which subsequently activates protein kinase D1 (PKD1). Through phosphorylating the C-terminals of the NMDAR GluN2 subunits, PKD1 down-regulates the activity of remaining (non-internalized) surface NMDARs. The knockdown of PKD1 does not affect the DHPG-induced inhibition of AMPA receptor-mediated miniature excitatory post-synaptic currents (mEPSCs) but prevents the DHPG-induced inhibition of NMDAR-mediated mEPSCs in vitro. Thus, we investigated the in vivo effects of bilateral infusions of DHPG into the hippocampal CA1 area of rats in the Morris water maze (MWM) and the novel object discrimination (NOD) tests. Methods A total of 300 adult male Sprague Dawley rats (250±280 g) were used for behavioral tests. One hundred ninety four were used in MWM test and the other 106 rats in the NOD test. Following one week of habituation to the vivarium, rats were bilaterally implanted under deep anesthesia with cannulas aimed at the CA1 area of the hippocampus (CA1 coordinates in mm from Bregma: AP -3.14; lateral +/-2; DV -3.0). Through implanted cannulas artificial cerebrospinal fluid (ACSF), the group1 mGluR antagonist 6-Methyl-2-(phenylethynyl)pyridine (MPEP), the dynamin-dependent internalization inhibitor Dynasore, or the PKD1 Hospital for Sick Children. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. inhibitor CID755673 were infused into the bilateral hippocampal CA1 areas (2 μL per side, over 5 min). The effects of these infusions and the effects of PKD1 knockdown were examined in MWM or NOD test. Results DHPG infusion increased the latency to reach the platform in the MWM test and reduced the preference for the novel object in the NOD task. We found that the DHPG effects were dose-dependent and could be maintained for up to 2 days. Notably, these effects could be prevented by pre-infusion of the group1 mGluR antagonist MPEP, the dynamin-dependent internalization inhibitor Dynasore, the PKD1 inhibitor CID755673, or by PKD1 knockdown in the hippocampal CA1 area. Conclusion Altogether, these findings provide direct evidence that PKD1-mediated signaling may play a critical role in the induction of learning and memory impairments by DHPG infusion into the hippocampal CA1 area. Introduction Hippocampal neurons have been found to play an important role in learning and memory functions of animals and humans. Increasing amounts of data have documented that the glutamate receptor-mediated signaling in the hippocampus plays crucial roles in the regulation of learning and memory. Up- or down-regulation of NMDA type of glutamate receptors in hippocampal neurons, for example, may lead to improvements or deficits in spatial memory of rodents [1±5]. Furthermore, preventing the hypofunction of NMDARs by al (...truncated)


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Wei Wang, Florian Duclot, Bradley R. Groveman, Nicole Carrier, Haifa Qiao, Xiao-Qian Fang, Hui Wang, Wenkuan Xin, Xing-Hong Jiang, Michael W. Salter, Xin-Sheng Ding, Mohamed Kabbaj, Xian-Min Yu. Hippocampal protein kinase D1 is necessary for DHPG-induced learning and memory impairments in rats, PLOS ONE, 2018, Volume 13, Issue 4, DOI: 10.1371/journal.pone.0195095