Am. J. Respir. Cell Mol. Biol.,
Volume 25, Number 1, July, 2001 98-103
Molecular and Biochemical Characterization of a CNP-Sensitive Guanylyl
Cyclase in Bovine Tracheal Smooth Muscle
Adolfo
Borges,
Sinaí
Sánchez de Villarroel,
Nena J.
Winand,
Itala
Lippo de Bécemberg,
Marcelo J.
Alfonzo,
and
Ramona
González de Alfonzo
Sección de Biomembranas, Instituto de Medicina Experimental, Facultad de Medicina, Universidad Central de Venezuela, Caracas,
Venezuela; and Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, New York
Muscarinic activation of bovine tracheal smooth muscle (BTSM)
is involved in cyclic guanosine monophosphate (cGMP) production mediated through soluble (sGC) and membrane-bound (mGC) guanylyl cyclases. A muscarinic- and NaCl-sensitive mGC exists in BTSM regulated by muscarinic receptors
coupled to G proteins. To identify the mGCs expressed in
BTSM, reverse transcriptase/polymerase chain reaction (RT-PCR) from total RNA was performed using degenerate oligonucleotides for amplification of a region conserved among GC
catalytic domains. Cloning of amplification products revealed that 76% of all BTSM GC transcripts corresponded to the sGC
1 subunit and 24% to the B-type (C-type NP 1-22 [CNP]-sensitive) GC receptor. cGMP production by BTSM membrane and
soluble fractions confirmed that sGC activity is 3-fold with respect to mGC activity. RT-PCR using specific oligonucleotides
revealed that A (atrial NP-sensitive) and C (guanylin-sensitive)
mGC subtypes are also expressed in BTSM. Stimulation of basal
plasma membrane GC activity by CNP was higher than that by
ANP, whereas guanylin showed no effect, indicating that
CNP-sensitive guanylyl cyclase (GC-B) is the predominant
functional BTSM mGC subtype. Strong adenosine triphosphate inhibition of CNP-stimulated mGC activity supports the
finding that the tracheal mGC isoform belongs to the natriuretic peptide-sensitive mGCs. Additionally, CNP was able to
reverse the chloride inhibition of BTSM mGC activity, suggesting that this is a novel G protein-coupled GC-B receptor.
Abbreviations: atrial NP 1-28, ANP; adenosine triphosphate, ATP; brain
NP 1-26, BNP; bovine serum albumin, BSA; bovine tracheal smooth muscle, BTSM; complementary DNA, cDNA; cyclic guanosine monophosphate, cGMP; C-type NP 1-22, CNP; C-type NP 1-53, CNP-53; dithiothreitol, DTT; guanylyl cyclase, GC; ANP-sensitive guanylyl cyclase, GC-A;
CNP-sensitive guanylyl cyclase, GC-B; Escherichia coli enterotoxin/guanylin-sensitive guanylyl cyclase, GC-C; guanosine triphosphate, GTP;
membrane-bound guanylyl cyclase, mGC; natriuretic peptide, NP; 1H-
[1,2,4]oxadiazolo[4,3-
]quinoxalin-1-one, ODQ; polymerase chain reaction, PCR; phenylmethylsulfonyl fluoride, PMSF; reverse transcriptase/
polymerase chain reaction, RT-PCR.