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Fibroblast and epidermal growth factor receptor expression in Xenopus oocytes displays distinct calcium oscillatory
E Browaeys-Poly1, K Cailliau, J P Vilain
1Université des Sciences et Technologies de Lille, Laboratoire de Biologie du Développement, Unité de Dynamique des Cellules Embryonnaires et Cancéreuses, Bâtiment SN3, 59655 Villeneuve D'Ascq Cedex, France.
Abstract:
Electrophysiological study performed with the voltage clamp technique was used to examine the intracellular calcium pathway activated by tyrosine kinase receptor members. Three FGF receptors from Pleurodeles PR1, PR3, PR4, homologs to human receptors, and the human EGF receptor were expressed in Xenopus oocytes. Under FGF1, FGF2 and FGF4 stimulation, PR1 and PR3 display a one phase inward chloride calcium dependent current superimposed by sustained oscillations, whereas PR4 did not show any oscillations. These currents were dependent on intracellular calcium mobilisation, as the responses were reduced by caffeine (10 mM). Solely PR4 responses were affected by an extracellular calcium depleted solution suggesting the involvement of concomitant extracellular and intracellular calcium intervention in the calcium chloride current, whereas PR1 and PR3 did not. Under EGF stimulation, the EGF receptor elicits a two component inward current composed of an undelayed rapid transient dependent on intracellular calcium store recruitment followed by a second slower current dependent on calcium influx. The specific pattern and amplitude of the calcium oscillations induced by the combinatorial action of growth factors on their receptors could be relevant in numerous calcium dependent cell functions.
Insights
This study investigated calcium signaling pathways activated by fibroblast growth factor (FGF) and epidermal growth factor (EGF) receptors in Xenopus oocytes. Findings reveal distinct calcium mobilization patterns influencing cell functions.
Area of Science:
- Cellular and Molecular Biology
- Neuroscience
- Biochemistry
Background:
- Tyrosine kinase receptors, including fibroblast growth factor (FGF) and epidermal growth factor (EGF) receptors, play critical roles in cellular signaling.
- Intracellular calcium (Ca2+) dynamics are fundamental to numerous cell functions, including proliferation, differentiation, and neurotransmission.
Purpose of the Study:
- To investigate the intracellular calcium (Ca2+) pathways activated by specific FGF receptors (PR1, PR3, PR4) and the human EGF receptor.
- To characterize the distinct Ca2+ mobilization patterns induced by FGF and EGF receptor stimulation.
Main Methods:
- Electrophysiological studies using the voltage clamp technique in Xenopus oocytes expressing FGF receptors (PR1, PR3, PR4) and human EGF receptor.
- Stimulation with FGF1, FGF2, FGF4, and EGF growth factors.
- Assessment of Ca2+-dependent chloride currents and oscillations, and effects of caffeine and extracellular Ca2+ depletion.
Main Results:
- FGF receptors PR1 and PR3 exhibited Ca2+-dependent inward chloride currents with sustained oscillations under FGF stimulation, unlike PR4.
- PR4 responses were modulated by both intracellular and extracellular Ca2+, while PR1 and PR3 primarily relied on intracellular Ca2+ mobilization.
- EGF receptor stimulation elicited a biphasic current involving intracellular Ca2+ store recruitment followed by Ca2+ influx.
Conclusions:
- Distinct Ca2+ mobilization patterns are triggered by different tyrosine kinase receptors (FGF vs. EGF) and receptor subtypes.
- The specific characteristics of Ca2+ oscillations induced by growth factor-receptor interactions are crucial for various Ca2+-dependent cellular processes.
- This research provides insights into the complex role of calcium signaling in cell function and potential therapeutic targets.