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

Jerid W. Robinson, Deborah M. Dickey, Kohji Miura, Toshimi Michigami, Keiichi Ozono, Lincoln R. Potter

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)375-382
Number of pages8
JournalBone
Volume56
Issue number2
DOIs
StatePublished - Oct 2013

Bibliographical note

Funding Information:
Grant-in Aid (21,922) from the University of Minnesota Graduate School to LRP and the National Institute of Arthritis and Musculoskeletal and Skin Diseases Training Grant T32AR050938 to JWR supported this work.

Keywords

  • Achondroplasia
  • Bone growth
  • CGMP
  • Dwarfism
  • Guanylate cyclase
  • Natriuretic peptides

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