报告题目：Peptide Amidation, Ciliogenesis and the Secretion of Bioactive Amidated Products byChlamydomonas
报 告 人：Stephen King教授
Stephen King，1982年在英国伦敦大学学院植物和微生物系获得博士学位。现为美国康涅狄格大学健康中心教授，电子显微镜中心主任。主要研究微藻中纤毛的组装、结构和运动。目前发表文章100余篇，研究成果分别发表在eLife，Proceedings of the National Academy of Sciences USA，American Journal of Human Genetics，Nature Genetics等杂志上。
Conversion of C-terminal glycine residues into amides is required for the bioactivity of many secreted peptides involved in intercellular communication (e.g. vasopressin, oxytocin etc.). This reaction is catalyzed only by the transmembrane protein peptidylglycinea-amidating monooxygenase (PAM).Chlamydomonasexpresses all the proteases needed for peptide precursor processing and active PAM which is found both in the Golgi and in cilia; the PAM catalytic domains are located in the lumen of the secretory pathway and on the external face of cilia. Although an integral membrane protein, ciliary PAM is also tightly associated with the axoneme as is polycystin-2. Lack of PAM results in defects in secretion, aberrant transition zone assembly and the formation of very short ciliary stubs that lack doublet microtubules and are filled with intraflagellar transport material.Chlamydomonascilia act as secretory organelles releasing vesicular ectosomes that are bioactive. Although absent from ectosomes isolated from vegetative cells, PAM is present in ectosomes from mating gametes indicating that the PAM-axoneme association is tightly regulated during the sexual cycle. Matinectosomes also contain amidated products generated by PAM and one of these acts to control the motile behavior of gametes. Together, our data suggest that peptide amidation is a key requirement for ciliogenesis and that cilia represent a previously unrecognized pathway by which amidated bioactive products involved in cell-cell communication are secreted.