Production and sorting of transgenic, modified human parathyroid hormone in vivo in rat salivary glands.

Polarized salivary epithelial cells can sort secretory proteins towards either the basolateral or apical pole. Transgenic human parathyroid hormone (hPTH) exclusively sorts apically in rat submandibular glands. To help understand this specific process we modified the hPTH cDNA sequence and delivered the cDNAs to glands in vivo using adenoviral (Ad) vectors. The Ad vectors encoded: (1) the native form of hPTH (Ad.pre-pro-hPTH1-84), (2) the native sequence, but with the pro-segment deleted (Ad.pre-hPTH1-84), and (3) a sequence containing the pre-segment followed by the first 34 amino acids of hPTH (Ad.pre-hPTH1-34). hPTH production and sorting were studied after two days. All constructs were effectively transcribed in targeted glands. However, the pre-hPTH1-84 modification led to reduced hPTH secretion and production, while no immunoreactive hPTH resulted from pre-hPTH1-34 cDNA infusion. The pre-hPTH1-84 modification had no effect on apical sorting. These in vivo results show that the signal responsible for hPTH's apical sorting does not reside in the pro-segment and that deleting both the pro-segment and the carboxyl-terminal region severely impairs post-translational processing of hPTH.