Related Experiment Videos
Insulin and insulin-like growth factor-I inhibit the L-type calcium channel current in rat pinealocytes
1Department of Medicine, University of Alberta, Edmonton, Canada.
Abstract:
Tyrosine phosphorylation has recently been shown to modulate ion channel activity. In the present study, the effect of growth factors on the L-type Ca2+ channel current in rat pinealocytes was investigated using the whole cell version of the patch clamp technique. Both insulin and insulin-like growth factor-I (IGF-I) inhibited the L-type Ca2+ channel current. This inhibition was dependent on concentration, with median effective concentration (EC50) values of 60 nM for insulin and 0.14 nM for IGF-I. Heat-inactivated insulin or IGF-I had no effect on the L-type Ca2+ channel current. The presence of anti-IGF-I receptor antibodies blocked the inhibitory effect of IGF-I on the L-type Ca2+ channel current. Two other growth factors, nerve growth factor and epidermal growth factor, had no effect on this current. The effects of insulin and IGF-I were blocked by lavendustin A, a tyrosine kinase inhibitor. Calphostin C, a protein kinase C inhibitor, attenuated the effect of insulin and IGF-I, whereas wortmannin, a phosphatidylinositol 3-kinase inhibitor, was ineffective. These observations indicate that insulin and IGF-I inhibit the L-type Ca2+ channel current in rat pinealocytes, and that tyrosine phosphorylation is involved in these effects of insulin and IGF-I.
Insights
Insulin and insulin-like growth factor-I (IGF-I) inhibit L-type calcium channel currents in rat pinealocytes. This effect involves tyrosine phosphorylation, highlighting a key signaling pathway in ion channel regulation.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Tyrosine phosphorylation is increasingly recognized as a regulator of ion channel function.
- L-type calcium channels play crucial roles in cellular signaling and function, including in pinealocytes.
Purpose of the Study:
- To investigate the effects of growth factors, specifically insulin and IGF-I, on L-type calcium channel currents in rat pinealocytes.
- To elucidate the signaling pathways, particularly tyrosine phosphorylation, involved in mediating these effects.
Main Methods:
- Whole-cell patch clamp technique was employed to measure L-type calcium channel currents.
- Concentration-response relationships were determined for insulin and IGF-I.
- Involvement of specific signaling molecules was assessed using inhibitors and antibodies (e.g., lavendustin A, calphostin C, anti-IGF-I receptor antibodies).
Main Results:
- Both insulin and IGF-I significantly inhibited the L-type calcium channel current in a dose-dependent manner (EC50 values: 60 nM for insulin, 0.14 nM for IGF-I).
- Heat-inactivated growth factors and other growth factors (NGF, EGF) did not affect the current.
- The inhibitory effects were blocked by a tyrosine kinase inhibitor (lavendustin A) and attenuated by a protein kinase C inhibitor (calphostin C), but not by a PI3K inhibitor (wortmannin).
- Anti-IGF-I receptor antibodies blocked IGF-I's inhibitory effect.
Conclusions:
- Insulin and IGF-I exert an inhibitory effect on L-type calcium channel current in rat pinealocytes.
- Tyrosine phosphorylation is a critical component of the signaling cascade mediating these inhibitory effects.
- These findings reveal a novel mechanism of growth factor-mediated regulation of ion channel activity via tyrosine kinase pathways.