Sequences within the C-terminus of the metabotropic glutamate receptor, mGluR5, are responsible for inner nuclear membrane localization [Cell Biology]

Traditionally G-protein coupled receptors (GPCR) are thought to be located on the cell surface where they transmit extracellular signals to the cytoplasm. However recent studies indicate that some GPCRs are also localized to various subcellular compartments such as the nucleus where they appear required for various biological functions. For example, the metabotropic glutamate receptor 5, mGluR5, is concentrated at the inner nuclear membrane (INM) where it mediates Ca2+ changes in the nucleoplasm by coupling with Gq/11. Here we identified a region within the C-terminal domain (amino acids 852-876) which is necessary and sufficient for INM localization of the receptor. Because these sequences do not correspond to known NLS motifs they represent a new motif for INM trafficking. mGluR5 is also trafficked to the PM where it undergoes re-cycling/degradation in a separate receptor pool, one that does not interact with the nuclear mGluR5 pool. Finally, our data suggest that once at the INM, mGluR5 is stably retained via interactions with molecular structures such as chromatin and nuclear Lamins. Thus mGluR5 is perfectly positioned to regulate nucleoplasmic Ca2+ in situ.

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