| Summary: | 碩士 === 國立陽明大學 === 神經科學研究所 === 94 === Cyclic AMP (cAMP) is an important second messenger. The variety of potential regulation of cAMP synthesis and degradation are due to the multiplicity of phosphodiesterases and adenylyl cyclases (ACs) isoforms. Characterization of AC regulation is therefore important. AC is an ATP-pyrophosphate lyase that converts ATP into cAMP and pyrophosphate upon stimulation. To date, 9 mammalian membrane-bound ACs have been identified. They exhibit similar structures: two hydrophobic domains (each contains 6 transmembrane spans) and three cytosolic domains (N- and C1 and C2). They are activated by extracellular G protein-coupled receptors. My thesis focuses on the regulation of the type V adenylyl cyclase (AC5) by one of its binding partner, Ric8a. AC5 has the longest N-terminals (242 amino acids) among the AC family and is enriched in the striatum and the heart. We found that the N-terminal domain of AC5 (amino acids 1-215, designated AC5N21-215) interacted with Ric8a in the yeast two hybrid system. Ric8a is a protein conserved from C. elegans to mammalian. It’s a guanine nucleotide exchange factor (GEF) and participates in the Gαq signaling of C. elegans nervous system. It has been shown to play an important role in the synaptic signaling network and asymmetric division of C. elegans. We found that Ric8a was colocalized with AC5 in PC12 and HEK293T cells and suppressed AC5 activity evoked by forskolin. We found that Ric8a promoted the neurite outgrowth in Neuro2a cells via a Giα-dependent pathway. The N-terminus of AC5 (AC5N21-215) inhibited the Ric8a-induced neurite outgrowth. The suppressing effect of AC5 on neurite outgrowth induced by Ric8a also depended on Gi��. Collectively, interaction between AC5 and Ric8 might contribute to neuronal differentiation of Neuro2a.
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