Abstract
Natriuretic peptide receptors A (NPR-A) and B (NPR-B) mediate most effects of natriuretic peptides by synthesizing cGMP. ATP increases the activity of these receptors by an unknown mechanism. We recently reported that a nonhydrolyzable form of ATP, adenylyl imidodiphosphate (AMPPNP), stabilizes but is not required for the activation of NPR-A and NPR-B in membranes from highly overexpressing cells. Here, we repeated these studies on receptors expressed in endogenous settings. Kinetic analysis indicated that both AMPPNP and ATP dramatically decrease the apparent Km of both receptors for GTP but had little effect on the Vmax. The EC50 for AMPPNP decreased as substrate concentration increased whereas the magnitude of the effect was greater at lower GTP concentrations. ATP increased the activity of a mutant receptor containing glutamates substituted for all known phosphorylation sites similarly to the wild-type receptor, consistent with a phosphorylation independent mechanism. Finally, the putative ATP binding sites were investigated. Mutation of the ATP modulatory domain region had no effect, but mutation of K535A dramatically diminished ANP-dependent cyclase activity in a manner that was unresponsive to ATP. Mutation of the highly conserved 630-KSS to AAA (all alanines) resulted in an expressed receptor that had no detectable guanylyl cyclase activity. We conclude that ATP is not required for the initial activation of NPRs but does increase activity over time by reducing the apparent Km for GTP.
| Original language | English (US) |
|---|---|
| Journal | American Journal of Physiology - Endocrinology and Metabolism |
| Volume | 293 |
| Issue number | 6 |
| DOIs | |
| State | Published - Dec 1 2007 |
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Keywords
- Adenosine triphosphate
- Bone growth
- Cyclic guanosine monophosphate
- Guanosine triphosphate
- Guanylyl cyclase
- Heart failure
- Hypertension
- Michaelis-Menten constant
Cite this
Adenine nucleotides decrease the apparent Km of endogenous natriuretic peptide receptors for GTP. / Antos, Laura K.; Potter, Lincoln R.
In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 293, No. 6, 01.12.2007.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Adenine nucleotides decrease the apparent Km of endogenous natriuretic peptide receptors for GTP
AU - Antos, Laura K.
AU - Potter, Lincoln R
PY - 2007/12/1
Y1 - 2007/12/1
N2 - Natriuretic peptide receptors A (NPR-A) and B (NPR-B) mediate most effects of natriuretic peptides by synthesizing cGMP. ATP increases the activity of these receptors by an unknown mechanism. We recently reported that a nonhydrolyzable form of ATP, adenylyl imidodiphosphate (AMPPNP), stabilizes but is not required for the activation of NPR-A and NPR-B in membranes from highly overexpressing cells. Here, we repeated these studies on receptors expressed in endogenous settings. Kinetic analysis indicated that both AMPPNP and ATP dramatically decrease the apparent Km of both receptors for GTP but had little effect on the Vmax. The EC50 for AMPPNP decreased as substrate concentration increased whereas the magnitude of the effect was greater at lower GTP concentrations. ATP increased the activity of a mutant receptor containing glutamates substituted for all known phosphorylation sites similarly to the wild-type receptor, consistent with a phosphorylation independent mechanism. Finally, the putative ATP binding sites were investigated. Mutation of the ATP modulatory domain region had no effect, but mutation of K535A dramatically diminished ANP-dependent cyclase activity in a manner that was unresponsive to ATP. Mutation of the highly conserved 630-KSS to AAA (all alanines) resulted in an expressed receptor that had no detectable guanylyl cyclase activity. We conclude that ATP is not required for the initial activation of NPRs but does increase activity over time by reducing the apparent Km for GTP.
AB - Natriuretic peptide receptors A (NPR-A) and B (NPR-B) mediate most effects of natriuretic peptides by synthesizing cGMP. ATP increases the activity of these receptors by an unknown mechanism. We recently reported that a nonhydrolyzable form of ATP, adenylyl imidodiphosphate (AMPPNP), stabilizes but is not required for the activation of NPR-A and NPR-B in membranes from highly overexpressing cells. Here, we repeated these studies on receptors expressed in endogenous settings. Kinetic analysis indicated that both AMPPNP and ATP dramatically decrease the apparent Km of both receptors for GTP but had little effect on the Vmax. The EC50 for AMPPNP decreased as substrate concentration increased whereas the magnitude of the effect was greater at lower GTP concentrations. ATP increased the activity of a mutant receptor containing glutamates substituted for all known phosphorylation sites similarly to the wild-type receptor, consistent with a phosphorylation independent mechanism. Finally, the putative ATP binding sites were investigated. Mutation of the ATP modulatory domain region had no effect, but mutation of K535A dramatically diminished ANP-dependent cyclase activity in a manner that was unresponsive to ATP. Mutation of the highly conserved 630-KSS to AAA (all alanines) resulted in an expressed receptor that had no detectable guanylyl cyclase activity. We conclude that ATP is not required for the initial activation of NPRs but does increase activity over time by reducing the apparent Km for GTP.
KW - Adenosine triphosphate
KW - Bone growth
KW - Cyclic guanosine monophosphate
KW - Guanosine triphosphate
KW - Guanylyl cyclase
KW - Heart failure
KW - Hypertension
KW - Michaelis-Menten constant
UR - http://www.scopus.com/inward/record.url?scp=37149013706&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=37149013706&partnerID=8YFLogxK
U2 - 10.1152/ajpendo.00321.2007
DO - 10.1152/ajpendo.00321.2007
M3 - Article
C2 - 17848634
AN - SCOPUS:37149013706
VL - 293
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
SN - 0363-6143
IS - 6
ER -