Loss-of-function and gain-of-function mutations of calcium-sensing receptor: functional analysis and the effect of allosteric modulators NPS R-568 and NPS 2143.

Abstract

OBJECTIVE:

Activating mutations in the calcium-sensing receptor (CASR) gene cause autosomal dominant hypoparathyroidism, and heterozygous inactivating CASR mutations cause familial hypocalciuric hypercalcemia. Recently, there has been a focus on the use of allosteric modulators to restore the functional activity of mutant CASRs. In this study, the effect of allosteric modulators NPS R-568 and NPS 2143 on CASR mutants was studied in vitro.

METHODS:

DNA sequence analysis of the CASR gene was undertaken in autosomal dominant hypoparathyroidism and familial hypocalciuric hypercalcemia Japanese patients, and the functional consequences for the Gi-MAPK pathway and cell surface expression of CASR were determined. Furthermore, we studied the effect of NPS R-568 and NPS 2143 on the signal transduction activity and cell surface expression of each mutant CASR.

RESULTS:

We identified 3 activating mutations (S122C, P569H, and I839T) and 2 inactivating mutations (A110T and R172G) in patients. The activating and inactivating mutations caused leftward and rightward shifts, respectively, in the dose-response curves of the signaling pathway. NPS R-568 rescued the signal transduction capacity of 2 inactivating mutants without increasing cell surface expression levels. NPS 2143 suppressed the enhanced activity of the activating mutants without altering cell surface expression levels, although A843E, which is a constitutively active mutant, was suppressed to a lesser degree.

CONCLUSIONS:

We have identified 4 novel mutations of CASR. Moreover, our results indicate that allosteric modulators can restore the activity of the loss- and gain-of-function mutant CASRs, identified in this study.

• Authors: Akie Nakamura, Tomoyuki Hotsubo, Keiji Kobayashi, Hiroshi Mochizuki, Katsura Ishizu, Toshihiro Tajima
• Journal: The Journal of clinical endocrinology and metabolism (J Clin Endocrinol Metab) Vol. 98 Issue 10 Pg. E1692-701 (Oct 2013) ISSN: 1945-7197 [Electronic] United States
• PMID: 23966241 (Publication Type: Journal Article)

Chemical References

• Receptors, Calcium-Sensing

Topics

• Child
• Humans
• Hypercalcemia (congenital, genetics)
• Hypoparathyroidism (genetics)
• Infant
• Infant, Newborn
• Mutation
• Receptors, Calcium-Sensing (genetics)