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Activation of M3 muscarinic acetylcholine receptors inhibits voltage-dependent calcium influx in small cell lung carcinoma. J Biol Chem 1990 Jan 25;265(3):1443-7

Date

01/25/1990

Pubmed ID

2153134

Scopus ID

2-s2.0-0025192955 (requires institutional sign-in at Scopus site)   33 Citations

Abstract

Small cell carcinoma of the lung (SCC) expresses several characteristics of neuronal cells, including voltage-gated Ca2+ channels (VGCC), and also expresses muscarinic acetylcholine receptors (mAChR). In testing the possibility that VGCC may be functionally coupled to mAChR in SCC cell lines, we found that depolarization-dependent Ca2+ influx was inhibited by carbachol (IC50 = 0.78 microM) and oxotremorine (IC50 = 0.69 microM). Equilibrium dissociation constants for several mAChR antagonists indicated that a mAChR of M3 subtype was involved. Exposure of SCC to carbachol induced the hydrolysis of phosphoinositides and increased the cytosolic free Ca2+ concentration ([Ca2+]i). The carbachol-mediated inhibition of depolarization-dependent Ca2+ influx did not directly correlate with increased [Ca2+]i but did correlate with inositol poly-phosphate generation. The protein kinase C activators phorbol 12-myristate 13-acetate or 1-oleoyl-2-acetyl-sn-glycerol neither mimicked nor amplified the inhibitory effect of carbachol on Ca2+ influx. However, phorbol 12-myristate 13-acetate suppressed the carbachol-induced inositol polyphosphate generation and inhibition of depolarization-dependent Ca2+ influx. The inactive compound 4 alpha-phorbol had no effect. These data suggest that the inhibition of VGCC caused by carbachol is not due to protein kinase C activation, but rather is due to events mediated by inositol polyphosphates. This is the first documentation of a role for phosphoinositide hydrolysis in the functional coupling of mAChR and VGCC. The expression of M3 mAChR functionally coupled to VGCC could have therapeutic implications for SCC, in light of recent demonstrations that cell proliferation can be influenced by activation of neurotransmitter receptors.

Author List

Williams CL, Lennon VA

Author

Carol L. Williams PhD Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Calcium
Calcium Channels
Carbachol
Carcinoma, Small Cell
Cytoplasm
Humans
In Vitro Techniques
Inositol Phosphates
Ion Channel Gating
Lung Neoplasms
Membrane Potentials
Parasympatholytics
Potassium
Protein Kinase C
Receptors, Muscarinic
Tumor Cells, Cultured