Role of tachykinin neurokinin 3 receptor within the nuclei of neurons in the paraventricular nucleus of the hypothalamus and its properties of translocation, The

Bell, Sean
Tachykinin neurokinin 3 receptor (NK3R) is a G protein binding receptor (GPCR) widely expressed within the magnocellular neurons of the supraoptic nuclei (SON) and the paraventricular nuclei (PVN) of the hypothalamus. Furthermore, hyperosmolarity causes the release of the ligand and the internalization of NK3R into the cytoplasm. Interestingly, NK3R was further trafficked into the nucleus. Our goal is to determine the co-localization of NK3R with histone H4 within the nucleus. Rats were given an (IG) load of 2 M NaCl, allowed to survive for 40 minutes and then sacrificed. Immuno-electron microscopy was used to determine co-localization. Antibodies were used against H4 or NK3R. Each antibody was visualized by administering a secondary antibody attached to either a 6 nm or 15 nm gold bead. Interestingly, confocal microscopy showed NK3R was further transported into the nuclei of hypothalamic neurons. We used double immuno- electron microscopy to determine if NK3R associates with chromatin following transport into the nucleus. We found that NK3R were co-localized with histone. The NK3R is unique in the tackykinin family in that it is the only receptor that is reported to contain a nuclear localization sequence (NLS). Furthermore, no other GPCR has been shown to interact with chromatin, in vivo, in an activity-dependent manner. The significance of the NK3Rs translocation and its role within the nucleus is still being investigated.
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