A human skeletal overgrowth mutation increases maximal velocity and blocks desensitization of guanylyl cyclase-B

Abstract

C-type natriuretic peptide (CNP) increases long bone growth by stimulating guanylyl cyclase (GC)-B/NPR-B/NPR2. Recently, a Val to Met missense mutation at position 883 in the catalytic domain of GC-B was identified in humans with increased blood cGMP levels that cause abnormally long bones. Here, we determined how this mutation activates GC-B. In the absence of CNP, cGMP levels in cells expressing V883M-GC-B were increased more than 20 fold compared to cells expressing wild-type (WT)-GC-B, and the addition of CNP only further increased cGMP levels 2-fold. In the absence of CNP, maximal enzymatic activity (Vmax) of V883M-GC-B was increased 15-fold compared to WT-GC-B but the affinity of the enzymes for substrate as revealed by the Michaelis constant (Km) was unaffected. Surprisingly, CNP decreased the Km of V883M-GC-B 10-fold in a concentration dependent manner without increasing Vmax. Unlike the WT enzyme the Km reduction of V883M-GC-B did not require ATP. Unexpectedly, V883M-GC-B, but not WT-GC-B, failed to inactivate with time. Phosphorylation elevated but was not required for the activity increase associated with the mutation because the Val to Met substitution also activated a GC-B mutant lacking all known phosphorylation sites. We conclude that the V883M mutation increases maximal velocity in the absence of CNP, eliminates the requirement for ATP in the CNP-dependent Km reduction, and disrupts the normal inactivation process.

Dephosphorylation is the mechanism of fibroblast growth factor inhibition of guanylyl cyclase-B

“…In humans, genetic mutations that inactivate both alleles encoding GC-B cause acromesomelic dysplasia, type Maroteaux (AMDM) dwarfism [6]. Conversely, mutations that increase CNP expression [7, 8] or mutations that activate a single GC-B allele in the absence of CNP cause skeletal overgrowth [9–11]. CNP levels in plasma are also predictive of longitudinal bone growth [12, 13].…”

Heterozygous Mutations in Natriuretic Peptide Receptor-B (NPR2) Gene as a Cause of Short Stature

“…On the other hand, overproduction of CNP due to a chromosomal translocation has been reported in association with a skeletal dysplasia characterized by tall stature [Bocciardi et al., ; Moncla et al., ]. In addition, gain‐of‐function mutations of NPR2 have been identified in several families and are associated with an overgrowth disorder with only mild skeletal features [Miura et al., ; Hannema et al., ; Robinson et al., ; Miura et al., ].…”

Dorsal root ganglion axon bifurcation tolerates increased cyclic GMP levels: the role of phosphodiesterase 2A and scavenger receptor Npr3

“…This is remarkable as increasing levels of CNP or Npr2 activity have been reported to affect human body height. For example, heterozygous gain-of-function mutations of Npr2 (Miura et al, 2012;Hannema et al, 2013;Robinson et al, 2013) or balanced translocations in chromosome 2 near the locus of the Nppc gene, resulting in overproduction of CNP, cause a tall stature in humans (Bocciardi et al, 2007;Moncla et al, 2007).…”