Platelet-derived Growth Factor (PDGF)-induced Ca2+ Signaling in the CG4 Oligodendroglial Cell Line and in Transformed Oligodendrocytes Expressing the β-PDGF Receptor

doi:10.1074/jbc.272.7.4351

Platelet-derived Growth Factor (PDGF)-induced Ca²⁺ Signaling in the CG4 Oligodendroglial Cell Line and in Transformed Oligodendrocytes Expressing the β-PDGF Receptor*

From the Department of Pharmacological and Physiological Sciences, The University of Chicago, Chicago, Illinois 60637

^‡ To whom correspondence should be addressed:
Dept. of Pharmacological and Physiological Sciences, The University of Chicago, 947 East 58th St., 60637 MC-0926, Chicago, IL
. Tel.: 773-702-3214; Fax: 773-702-5903.

Abstract

Ca²⁺ signaling induced by platelet-derived growth factor (PDGF) was investigated in the oligodendroglial cell lines CG4 and CEINGE clone 3, using fura-2 microfluorimetry and video imaging. CEINGE cl3 cells, immortalized with polyoma middle T antigen, were found to uniformly express the polyoma middle T antigen protein as well as 2′,3′-cyclic nucleotide 3′-phosphodiesterase, a specific marker for oligodendroglia. PDGF-BB induced both oscillatory and non-oscillatory Ca²⁺ responses in CEINGE cl3 cells as well as in CG4 cells, grown either as O-2A progenitors or differentiated oligodendrocytes. However, in CG4 cells the percentage of oscillatory Ca²⁺ responses was higher than that observed in CEINGE cl3 cells. In contrast, oscillatory Ca²⁺ responses were not observed in PC-12 cells transfected with β-PDGF receptor (PDGFR) or in NIH 3T3 fibroblasts. CG4 cells expressed only the α-PDGFR, whereas CEINGE cl3 cells expressed both α and β isoforms. When CEINGE cl3 cells were exposed to PDGF-AA, which binds only to the α-PDGFR, the percentage of oscillatory Ca²⁺ responses was higher than that observed after PDGF-BB stimulation. We previously reported that block of the enzyme sphingosine kinase, and a consequent increase in intracellular sphingosine levels in CEINGE cl3 cells caused an increase in the percentage of oscillatory Ca²⁺ responses induced by PDGF-BB. However, in CG4 cells block of sphingosine kinase did not increase the oscillatory Ca²⁺ response elicited by PDGF-BB, although the addition of exogenous sphingosine induced an oscillatory Ca²⁺ response in 77% of cells studied. We hypothesize that the α-PDGFR is less effective than the β-PDGFR in stimulating the activity of sphingosine kinase. The results also suggest that α- and β-PDGFRs may differently regulate sphingolipid metabolism.

Footnotes

↵* This work was supported by Public Health Service Grants DA-02121, MH-40165, NS-33502, and DA-02575. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

PDGF

platelet-derived growth factor

R

receptor

[Ca²⁺]_i

intracellular free Ca²⁺ concentration

PLC

phospholipase C

CNP

2′,3′-cyclic nucleotide 3′-phosphodiesterase

mT

polyoma middle T antigen

GalC

galactocerebroside

PBS

phosphate-buffered saline

DMEM

Dulbecco's modified Eagle's medium

SPP

sphingosine 1-phosphate.
- Received October 7, 1996.
- Revision received December 3, 1996.