Purkinje cell synaptic signaling and cerebellar function: Role of TRPC channels

• Applicant: Dr. Jana Hartmann
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2007 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 43598402

The seven members of the TRPC protein family form Ca2+-permeable cation channels that are activated by PLC-linked receptors. TRPC channels are abundantly expressed in the brain. However, their physiological functions in central neurons are largely unknown. In particular, virtually nothing is known about a possible involvement of TRPC channels in synaptic signaling. Like other types of neurons, cerebellar Purkinje cells express various types of TRPC channels. In addition, they highly express the PLC-coupled metabotropic glutamate receptor 1 (mGluR1). Synaptic activation of mGluR1 is crucial for Purkinje cell signaling and cerebellar function. Recently, it was claimed that TRPC1 is responsible for the mGluR1-mediated slow excitatory postsynaptic potential (sEPSP). However, in a preliminary analysis of knockout mice deficient for TRPC1 (in combination with TRPC4 and TRPC6) we found that the sEPSP persists in the absence of these three TRPC subunits. Interestingly, quantitative single cell RT-PCR analysis experiments suggest that TRPC3, but not TRPC1 is the by far dominating TRPC subunit in Purkinje cells. Our aim is to analyze the function of various TRPC channels in Purkinje cells. In view of our preliminary results, we are particularly interested in TRPC3. Therefore, we will generate a Purkinje cell-specific TRPC3-deficient mouse strain. This and the other already available TRPC specific mouse mutants will be tested for alterations in their cerebellar function. Cellular analyses, including patch clamp recordings and calcium imaging, will be performed in cerebellar slices from wild type and mutant mice. We will clarify whether the mGluR1-mediated sEPSP is mediated by members of the TRPC channel subfamily and which of the different TRPC subunits contribute to it. We will investigate Ca2+ homeostasis and Ca2+ signaling in Purkinje cells in the absence of different TRPC subunits. We will also investigate the role of TRPC channels for Ca2+ store refilling in Purkinje cells. Finally, we will determine the role of TRPC channels for cerebellar LTD.

• DFG Programme: Research Grants
• Participating Person: Professor Dr. Arthur Konnerth