Nuclear localization of the type 1 PTH/PTHrP receptor in rat tissues

The localization of PTH/PTH-related peptide (PTHrP) receptor (PTHR) has tra ditionally been performed by autoradiography, Specific polyclonal antibodie s to peptides unique to the PTHR are now available, which allow a more prec ise localization of the receptor in cells and tissues. We optimized the IHC procedure for the rat PTHR using 5-mu m sections of paraffin-embedded rat kidney, liver, small intestine, uterus, and ovary. Adjacent sections were a nalyzed for the presence of PTHR mRNA (by in situ hybridization) and PTHrP peptide. A typical pattern of staining for both receptor protein and mRNA w as observed in kidney in cells lining the proximal tubules and collecting d ucts. In uterus and gut, the receptor and its mRNA are present in smooth mu scle layers (PTHrP target) and in glandular cuboidal cells and surface colu mnar epithelium, This suggests that PTH, or more likely PTHrP, plays a role in surface/secretory epithelia that is as yet undefined. In the ovary, PTH R was readily detectable in the thecal layer of large antral follicles and oocytes, and was present in the cytoplasm and/or nucleus of granulosa cells , regions that also contained receptor transcripts. PTHR protein and mRNA w ere found in the liver in large hepatocytes radiating outward from central veins. Immunoreactive cells were also present around the periphery of the l iver but not within two or three cell layers of the surface. Clear nuclear localization of the receptor protein was present in liver cells in addition to the expected cytoplasmic/peripheral staining. PTHR immunoreactivity was present in the nucleus of some cells in every tissue examined. RT-PCR conf irmed the presence of PTHR transcripts in these same tissues. Examination o f the hindlimbs of PTHR gene-ablated mice showed no reaction to this antibo dy, whereas hindlimbs from their wild-type littermates stained positively. The results emphasize that the PTHR is highly expressed in diverse tissues and, in addition, show that the receptor protein itself can be localized to the cell nucleus. Nuclear localization of the receptor suggests that there is a role for PTH and/or PTHrP in the regulation of nuclear events, either on the physical environment (nucleoskeleton) or directly on gene expressio n.