Analysis of mutant platelet-derived growth factor receptors expressed in PC12 cells identifies signals governing sodium channel induction during neuronal differentiation.
The mechanisms governing neuronal differentiation, including the signals underlying the induction of voltage-dependent sodium (Na+) channel expression by neurotrophic factors, which occurs independent of Ras activity, are not well understood. Therefore, Na+ channel induction was analyzed in sublines of PC12 cells stably expressing platelet-derived growth factor (PDGF) beta receptors with mutations that eliminate activation of specific signalling molecules. Mutations eliminating activation of phosphatidylinositol 3-kinase (PI3K), phospholipase C gamma (PLC gamma), the GTPase-activating protein (GAP), and Syp phosphatase failed to diminish the induction of type II Na+ channel alpha-subunit mRNA and functional Na+ channel expression by PDGF, as determined by RNase protection assays and whole-cell patch clamp recording. However, mutation of juxtamembrane tyrosines that bind members of the Src family of kinases upon receptor activation inhibited the induction of functional Na+ channels while leaving the induction of type II alpha-subunit mRNA intact. Mutation of juxtamembrane tyrosines in combination with mutations eliminating activation of PI3K, PLC gamma, GAP, and Syp abolished the induction of type II alpha-subunit mRNA, suggesting that at least partially redundant signaling mechanisms mediate this induction. The differential effects of the receptor mutations on Na+ channel expression did not reflect global changes in receptor signaling capabilities, as in all of the mutant receptors analyzed, the induction of c-fos and transin mRNAs still occurred. The results reveal an important role for the Src family in the induction of Na+ channel expression and highlight the multiplicity and combinatorial nature of the signaling mechanisms governing neuronal differentiation.
Fanger
G R
GR
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Vaillancourt
R R
RR
Heasley
L E
LE
Montmayeur
J P
JP
Johnson
G L
GL
Maue
R A
RA
D000818:Animals; D000077214:Becaplermin; D002454:Cell Differentiation; D020690:GTPase-Activating Proteins; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000378:metabolism; D019278:Matrix Metalloproteinase 3 / Q000235:genetics; D009154:Mutation; D009414:Nerve Growth Factors / Q000494:pharmacology; D016501:Neurites / Q000378:metabolism; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D016716:PC12 Cells; D018408:Patch-Clamp Techniques; D019869:Phosphatidylinositol 3-Kinases; D051966:Phospholipase C gamma; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D020797:Receptor, Platelet-Derived Growth Factor beta; D017479:Receptors, Platelet-Derived Growth Factor / Q000235:genetics* / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D015222:Sodium Channels / Q000235:genetics / Q000502:physiology*; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D020703:ras GTPase-Activating Proteins
D020690:GTPase-Activating Proteins; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D009414:Nerve Growth Factors; D010982:Platelet-Derived Growth Factor; D011506:Proteins; D016760:Proto-Oncogene Proteins c-fos; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D015222:Sodium Channels; D020703:ras GTPase-Activating Proteins; D000077214:Becaplermin; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D020794:Receptor Protein-Tyrosine Kinases; D020797:Receptor, Platelet-Derived Growth Factor beta; D017479:Receptors, Platelet-Derived Growth Factor; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516727:Ptpn11 protein, rat; C509250:Ptpn6 protein, rat; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D019278:Matrix Metalloproteinase 3