Abstract
The PTH/PTHrP receptor (PTHR1) mediates the actions of parathyroid
hormone (PTH) and PTH-related peptide (PTHrP) by coupling this G protein-coupled
receptor (GPCR) to the alpha-subunit of the heterotrimeric stimulatory G protein
(Gsα) and thereby to the formation of cAMP. In growth plates,
PTHrP-dependent activation of the cAMP/PKA second messenger pathway
prevents the premature differentiation of chondrocytes into hypertrophic cells
resulting in delayed growth plate closure. Heterozygous mutations in
GNAS, the gene encoding Gsα, lead to a reduction in cAMP levels
in growth plate chondrocytes that is sufficient to cause shortening of
metacarpals and/or -tarsals, i. e. typical skeletal aspects of
Albright’s Hereditary Osteodystrophy (AHO). However, heterozygous
mutations in other genes, including those encoding PTHrP, PRKAR1A, PDE4D, and
PDE3A, can lead to similar or even more pronounced acceleration of skeletal
maturation that is particularly obvious in hands and feet, and reduces final
adult height. Genetic mutations other than those resulting in Gsα
haploinsufficiency thus reduce intracellular cAMP levels in growth plate
chondrocytes to a similar extent and thereby accelerate skeletal maturation.
Key words
PTH - PTHrP - PTH/PTHrP receptor - GNAS - alpha-subunit of the stimulatory G protein
- genetic disease - acrodysostosis - cAMP signaling pathway - PRKAR1A - PDE4D - PDE3A
- HDAC4