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Updated: Aug 17, 2026
Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells
Published on: October 1, 2010
Mitogens and oncogenes can block the induction of specific voltage-gated ion channels
Abstract:
The mechanisms underlying the ontogeny of voltage-gated ion channels in muscle are unknown. Whether expression of voltage-gated channels is dependent on mitogen withdrawal and growth arrest, as is generally true for the induction of muscle-specific gene products, was investigated in the BC3H1 muscle cell line by patch-clamp techniques. Differentiated BC3H1 myocytes expressed functional Ca2+ and Na+ channels that correspond to those found in T tubules of skeletal muscle. However, Ca2+ and Na+ channels were first detected after about 5 days of mitogen withdrawal. In order to test whether cellular oncogenes, as surrogates for exogenous growth factors, could prevent the expression of ion channels whose induction was contingent on mitogen withdrawal, BC3H1 cells were modified by stable transfection with oncogene expression vectors. Expression vectors containing v-erbB, or c-myc under the control of the SV40 promoter, delayed but did not prevent the appearance of functional Ca2+ and Na+ channels. In contrast, transfection with a Val12 c-H-ras vector, or cotransfection of c-myc together with v-erbB, suppressed the formation of functional Ca2+ and Na+ channels for greater than or equal to 4 weeks. Potassium channels were affected neither by mitogenic medium nor by transfected oncogenes. Thus, the selective effects of certain oncogenes on ion channel induction corresponded to the suppressive effects of mitogenic medium.
Insights
Muscle cell growth arrest is necessary for voltage-gated calcium (Ca2+) and sodium (Na+) channel development. Certain oncogenes can delay or suppress this channel expression, impacting muscle electrophysiology.
Area of Science:
- Cellular and Molecular Biology
- Neuroscience
- Muscle Physiology
Background:
- The developmental mechanisms of voltage-gated ion channels in muscle cells remain largely unknown.
- Muscle-specific gene expression is typically induced by mitogen withdrawal and growth arrest.
Purpose of the Study:
- To investigate if voltage-gated ion channel expression in muscle cells depends on mitogen withdrawal and growth arrest.
- To determine the role of cellular oncogenes in regulating ion channel ontogeny during muscle cell differentiation.
Main Methods:
- Utilized the BC3H1 muscle cell line for experiments.
- Employed patch-clamp techniques to detect functional ion channels.
- Transfected BC3H1 cells with various oncogene expression vectors (v-erbB, c-myc, Val12 c-H-ras).
Main Results:
- Differentiated BC3H1 myocytes exhibited functional Ca2+ and Na+ channels, appearing after approximately 5 days of mitogen withdrawal.
- Oncogenes v-erbB and c-myc individually delayed but did not prevent Ca2+ and Na+ channel appearance.
- Val12 c-H-ras or combined c-myc/v-erbB transfection suppressed functional Ca2+ and Na+ channel formation for over 4 weeks.
- Potassium channels were unaffected by mitogenic medium or oncogene expression.
Conclusions:
- Mitogen withdrawal and growth arrest are critical for the induction of functional Ca2+ and Na+ channels in muscle cells.
- Specific oncogenes, particularly Ras and combinations involving Myc, can significantly suppress voltage-gated ion channel development.
- Oncogene-mediated effects on ion channel induction mirror the suppressive impact of mitogenic conditions on muscle cell differentiation.
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