title: Loss of the transcriptional repressor PAG-3/Gfi-1 results in enhanced neurosecretion that is dependent on the dense-core vesicle membrane protein IDA-1/IA-2.
abstract: It is generally accepted that neuroendocrine cells regulate dense core vesicle (DCV) biogenesis and cargo packaging in response to secretory demands, although the molecular mechanisms of this process are poorly understood. One factor that has previously been implicated in DCV regulation is IA-2, a catalytically inactive protein phosphatase present in DCV membranes. Our ability to directly visualize a functional, GFP-tagged version of an IA-2 homolog in live Caenorhabditis elegans animals has allowed us to capitalize on the genetics of the system to screen for mutations that disrupt DCV regulation. We found that loss of activity in the transcription factor PAG-3/Gfi-1, which functions as a repressor in many systems, results in a dramatic up-regulation of IDA-1/IA-2 and other DCV proteins. The up-regulation of DCV components was accompanied by an increase in presynaptic DCV numbers and resulted in phenotypes consistent with increased neuroendocrine secretion. Double mutant combinations revealed that these PAG-3 mutant phenotypes were dependent on wild type IDA-1 function. Our results support a model in which IDA-1/IA-2 is a critical element in DCV regulation and reveal a novel genetic link to PAG-3-mediated transcriptional regulation. To our knowledge, this is the first mutation identified that results in increased neurosecretion, a phenotype that has clinical implications for DCV-mediated secretory disorders.
authors.affiliation: Experimental Medicine Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America. tcai@mail.nih.gov
authors.forename: Tao
authors.initials: T
authors.lastname: Cai
authors.forename: Hiroki
authors.initials: H
authors.lastname: Hirai
authors.forename: Tetsunari
authors.initials: T
authors.lastname: Fukushige
authors.forename: Ping
authors.initials: P
authors.lastname: Yu
authors.forename: Guofeng
authors.initials: G
authors.lastname: Zhang
authors.forename: Abner L
authors.initials: AL
authors.lastname: Notkins
authors.forename: Michael
authors.initials: M
authors.lastname: Krause