Structural and Physiologic Characterization of the Mid-region Secretory Species of Parathyroid Hormone-related Protein

doi:10.1074/jbc.271.40.24371

Structural and Physiologic Characterization of the Mid-region Secretory Species of Parathyroid Hormone-related Protein*

From the ^‡ Division of Endocrinology, Connecticut Veterans Affairs Medical Center, West Haven, Connecticut 06516,
^§ Section of Endocrinology, Yale University School of Medicine, New Haven Connecticut 06510,
^¶ Division of Nephrology, Cleveland Veterans Affairs Medical Center and Case Western Reserve Medical School, Cleveland Ohio 44106, and
^∥ Institute of Biological Sciences, University of Wales, Aberystwyth, SY23 3DD, United Kingdom

^″ To whom correspondence should be addressed:
Research 151C, VA Medical Center, 950 Campbell Ave., West Haven, CT 06516
. Tel.: 203-932-5711 (ext. 3389); Fax: 203-937-3829.

Abstract

Parathyroid hormone-related protein (PTHrP) is initially translated as a preprohormone which is posttranslationally processed to yield a family of mature secretory forms. Most attention has focused on the amino-terminal portion of the molecule which is homologous to parathyroid hormone. It is clear, however, that a mid-region species of PTHrP is posttranslationally cleaved from the highly conserved mid-region of PTHrP, and that the amino terminus of this peptide is Ala³⁸. The purposes of the current study were three: 1) to confirm that Arg³⁷ immediately preceding Ala³⁸ serves as a posttranslational processing site in the PTHrP precursor, 2) to determine the carboxyl terminus of the mid-region secretory species of PTHrP, and 3) to synthesize this authentic mid-region secretory form of PTHrP and determine whether it is biologically active. The results indicate that: 1) Arg³⁷ is indeed a processing site in the PTHrP precursor; 2) three distinct mid-region PTHrP species are generated by posttranslational processing, PTHrP(38-94)amide, PTHrP(38-95), and most likely, PTHrP(38-101); and 3) synthetic mid-region PTHrP(38-94)amide is active in four different biological systems. These studies confirm the finding that PTHrP is a prohormone. More importantly, they define a novel, biologically active highly conserved mid-region secretory form of PTHrP.

Footnotes

↵* This work was supported by the Department of Veterans Affairs, West Haven, CT, The American Physiological Society, Biotechnology and Biological Sciences Research Council Grant LR2/559, and National Institutes of Health Grants DK 47168 and DK 02229. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

PTHrP

parathyroid hormone-related protein

PTH

parathyroid hormone

PAM

peptidyl α-amidating mono-oxygenase

HPLC

high performance liquid chromatography

RIN

rat insulinoma

RIA

radioimmunoassay

PAGE

polyacrylamide gel electrophoresis.
- Received April 23, 1996.
- Revision received July 11, 1996.