PI(4,5)P2-dependent regulation of exocytosis by amisyn, the vertebrate-specific competitor of synaptobrevin 2.

The functions of nervous and neuroendocrine systems rely on fast and tightly regulated release of neurotransmitters stored in secretory vesicles through SNARE-mediated exocytosis. Few proteins, including tomosyn (STXBP5) and amisyn (STXBP6), were proposed to negatively regulate exocytosis. Little is known about amisyn, a 24-kDa brain-enriched protein with a SNARE motif. We report here that full-length amisyn forms a stable SNARE complex with syntaxin-1 and SNAP-25 through its C-terminal SNARE motif and competes with synaptobrevin-2/VAMP2 for the SNARE-complex assembly. Furthermore, amisyn contains an N-terminal pleckstrin homology domain that mediates its transient association with the plasma membrane of neurosecretory cells by binding to phospholipid PI(4,5)P2 However, unlike synaptrobrevin-2, the SNARE motif of amisyn is not sufficient to account for the role of amisyn in exocytosis: Both the pleckstrin homology domain and the SNARE motif are needed for its inhibitory function. Mechanistically, amisyn interferes with the priming of secretory vesicles and the sizes of releasable vesicle pools, but not vesicle fusion properties. Our biochemical and functional analyses of this vertebrate-specific protein unveil key aspects of negative regulation of exocytosis.

Detection and identification of viral pathogens in patients with hand, foot, and mouth disease by multilocus PCR, reverse-transcription PCR and electrospray ionization mass spectrometry.

BACKGROUND: Rapid detection and identification of viruses are important for early diagnosis and effective surveillance of hand, foot, and mouth disease (HFMD). We described a novel assay using multilocus PCR and reverse transcription-PCR coupled with electrospray ionization mass spectrometry (RT-PCR/ESI-MS) to simultaneously detect and identify human enterovirus A-D, adenovirus A-F, human herpesvirus 1-8, parvovirus B19 and polyomavirus. OBJECTIVES: To evaluate the accuracy and efficacy of the RT-PCR/ESI-MS method, to detect and type enterovirus from specimens of clinical diagnosed HFMD patients. STUDY DESIGN: In this study, 152 specimens of clinically diagnosed HFMD patients were studied by the assay using RT-PCR/ESI-MS method. The detection and typing of enterovirus by RT-PCR/ESI-MS were compared with results from reference molecular methods. RESULTS: The assay detected enteroviruses in 97 (63.8%) specimens, resulting in a sensitivity of 93.8% (95% CI: 91.8-95.7%) and a specificity of 87.5% (95% CI: 84.8-90.2%) compared with a reference clinical diagnostic test. Most enterovirus genotypes (65/84; 77%) determined by the platform were consistent with 5' UTR sequence analysis, and most misidentifications resulted from the virus library, which could be further improved by updating the enterovirus database. In addition to enteroviruses, herpesviruses, polyomaviruses, adenoviruses and human rhinoviruses were detected and identified in 55 (36%) HFMD specimens by RT-PCR/ESI-MS. CONCLUSION: With the capability of high throughput and detection and typing of multiple clinically relevant viruses simultaneously, RT-PCR/ESI-MS can be a rapid and robust laboratory tool for identifying viral pathogens.