Calcium channel upregulation in response to activation of neurotrophin and surrogate neurotrophin receptor tyrosine kinases

• Published in: Journal of neuroscience research Vol. 74; no. 1; pp. 23 - 36
• Main Authors: Black, Melony J., Woo, Yeunkyung, Rane, Stanley G.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.10.2003
• Subjects: Animals; calcium channel; Calcium Channels - biosynthesis; Enzyme Activation - physiology; Ion Channel Gating - physiology; Nerve Growth Factor - pharmacology; Nerve Growth Factors - metabolism; Nerve Growth Factors - physiology; NGF; PC12; PC12 Cells; PDGF; Platelet-Derived Growth Factor - pharmacology; Rats; Receptor Protein-Tyrosine Kinases - metabolism; Receptors, Nerve Growth Factor - metabolism; Receptors, Nerve Growth Factor - physiology; Signal Transduction - physiology; Up-Regulation - physiology
• ISSN: 0360-4012; 1097-4547
• DOI: 10.1002/jnr.10748

Modulation of calcium channel expression and function in the context of neurotrophin induced neuronal differentiation remains incompletely understood at a mechanistic level. We addressed this issue in the PC12 model neuronal system using patch clamp electrophysiology combined with ectopic expression of the human β platelet‐derived growth factor (βPDGF) receptor as a surrogate neurotrophin receptor system. PC12 cells ectopically expressing the human βPDGF receptor were treated with PDGF or nerve growth factor (NGF) for up to 7 days, and Ca2+ channel subtype expression was analyzed using selective pharmacological agents in both whole‐cell and cell‐attached single channel patch clamp configurations. PDGF‐induced upregulation of N‐ and P/Q‐type Ca2+ channel currents completely mimicked upregulation of these currents caused by NGF stimulation of the endogenous TrkA receptor tyrosine kinase (RTK). Neither PDGF nor NGF significantly altered L‐ or R‐type currents. Single channel recordings together with immunocytochemistry implied that growth factor‐induced increases in whole‐cell Ca2+ currents were a result of synthesis of new channels, and that whereas increased N channel density was apparent in the soma, additional P/Q channels distributed preferentially to extrasomal locations, most likely the proximal neurites. Finally, specific signaling‐deficient mutant forms of the βPDGF receptor were used to show that activation of Src, PI3‐kinase, RasGAP, PLCγ or SHP‐2 (some of which are implicated in certain other aspects of PC12 cell differentiation) by RTKs is not required for growth factor‐induced Ca2+ channel upregulation. In contrast, activation of the Ras‐related G‐protein Rap1 was found critical to this process. © 2003 Wiley‐Liss, Inc.