FIve distinct but related muscarinic receptors had been identified. These glycosylated proteins have single chains of 460 to 590 amino acids that
are thought to span the plasma membrane 7 times, creating 4 extracellular domains, 7 helical hydrophobic
transmembrane domains, and 4 intracellular domains. Each protein is the product of a different gene without introns in
the coding sequence, and the amino acid sequences in the receptor subtypes are remarkably homologous among different
animal species.
NCBI Summary:
The muscarinic cholinergic receptors belong to a larger family of G protein-coupled receptors. The functional diversity of these receptors is defined by the binding of acetylcholine to these receptors and includes cellular responses such as adenylate cyclase inhibition, phosphoinositide degeneration, and postassium channel mediation. Muscarinic receptors influence many effects of acetylcholine in the central and peripheral nervous system. The clinical implications of this receptor are unknown; however, stimulation of this receptor is known to increase cyclic AMP levels.
General function
Receptor
Comment
Cellular localization
Plasma membrane
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Ovarian function
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Soboloff J, et al 1995 reported the influence of the muscarinic agonist carbachol on intracellular Ca2+ in chicken
granulosa cells.
Mayerhofer A, et al 1992 reported that carbachol treatment increases intracellular free calcium concentrations in human
granulosa-lutein cells.
Although an early study in rats suggested an inhibitory effect of muscarinic cholinergic agents on progesterone production (Kasson et al., 1985), subsequent studies in human, bovine and chicken granulosa (-luteal) cells indicated a stimulatory effect of muscarinic agenets on progesterone and estogen biosynthesis (Luck et al, 1990; Li et al., 1992; Bodis et al., 1993).
Expression regulated by
Comment
Ovarian localization
Granulosa
Comment
Fritz S, et al 2001 reported the expression of muscarinic receptor types in the primate ovary
and evidence for nonneuronal acetylcholine synthesis.
Because luteinized human granulosa cells (GC) in culture express
functional MR, the authors have determined whether the group of the related MR
subtypes, M1R, M3R, and M5R, are present in vivo in human and rhesus monkey
ovaries. To this end, ribonucleic acids (RNAs) of different human and monkey
ovaries as well as RNAs from human GC and monkey oocytes were reverse
transcribed and subjected to PCR amplification, followed by sequencing of the
amplified complementary DNAs. Results obtained showed that M1R, M3R, and M5R
messenger RNAs are present in adult human and monkey ovaries; oocytes express
exclusively the M3R subtype, whereas GC express M1R and M5R.