|Budget Amount *help
¥12,900,000 (Direct Cost: ¥12,900,000)
Fiscal Year 2000: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1999: ¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 1998: ¥6,400,000 (Direct Cost: ¥6,400,000)
Prostaglandins (PGs) exert a variety of regulations of neuronal functions, such as hyperthermia and analgesia. Furthermore, it has been suggested that PGs play important roles in synaptic plasticity, including regulation of neurite outgrowth, modulation of memory consolidation and formation of synapses. However, molecular mechanisms for these neuronal functions of PGs are not yet understood. In this study, we have examined the intracellular signal transduction pathways of PGE receptor EP3 subtype, the most prominent receptor in CNS.
In PC12 cells, EP3 receptor induces neurite retraction and growth cone collapse. This action was mediated by small GTPase, Rho, and its downstream effector, Rho-kinase. Constitutively active RhoA and Rho-kinase induced neurite retraction. Therefore, activation of Rho-kinase is enough for the neurite retraction. We further examined a trimeric G protein coupled to EP3 receptor, linking to the Rho activation pathway. Among various trimericG proteins, α subunits of G12, G13 and Gq induced neurite retraction through the activation of Rho. We then examined which type of G protein was coupled to EP3 receptor, and revealed that EP3 receptor was specifically coupled to G13, leading to activation of Rho and induction of neurite retraction. Therefore, EP3 receptor induces neurite retraction via a G13-Rho-Rho-kinase pathway. One of the well-known neuronal actions of EP3 receptor is the inhibition of neurotransmitter release. We then examined the intracelular signal transduction pathway of EP3 receptor for the inhibition. In PC12 cells, EP3 receptor inhibited the high K-or bradykinin-induced dopamine release. Constitutively active α subunits of G12 and G13 and constitutively active RhoA, RhoA-V14, also inhibited the release. This inhibition by EP3 receptor was mediated by G13-Rho-Rho-kinase. Therefore, EP3 receptor plays an important role in the regulation of neuronal morphology and synaptic