title: Insight into insulin secretion from transcriptome and genetic analysis of insulin-producing cells of Drosophila.
abstract: Insulin-producing cells (IPCs) in the Drosophila brain produce and release insulin-like peptides (ILPs) to the hemolymph. ILPs are crucial for growth and regulation of metabolic activity in flies, functions analogous to those of mammalian insulin and insulin-like growth factors (IGFs). To identify components functioning in IPCs to control ILP production, we employed genomic and candidate gene approaches. We used laser microdissection and messenger RNA sequencing to characterize the transcriptome of larval IPCs. IPCs highly express many genes homologous to genes active in insulin-producing β-cells of the mammalian pancreas. The genes in common encode ILPs and proteins that control insulin metabolism, storage, secretion, β-cell proliferation, and some not previously linked to insulin production or β-cell function. Among these novelties is unc-104, a kinesin 3 family gene, which is more highly expressed in IPCs compared to most other neurons. Knockdown of unc-104 in IPCs impaired ILP secretion and reduced peripheral insulin signaling. Unc-104 appears to transport ILPs along axons. As a complementary approach, we tested dominant-negative Rab genes to find Rab proteins required in IPCs for ILP production or secretion. Rab1 was identified as crucial for ILP trafficking in IPCs. Inhibition of Rab1 in IPCs increased circulating sugar levels, delayed development, and lowered weight and body size. Immunofluorescence labeling of Rab1 showed its tight association with ILP2 in the Golgi of IPCs. Unc-104 and Rab1 join other proteins required for ILP transport in IPCs.
authors.affiliation: Department of Developmental Biology, Stanford University School of Medicine, Stanford, California 94305.
authors.forename: Jian
authors.initials: J
authors.lastname: Cao
authors.forename: Julie
authors.initials: J
authors.lastname: Ni
authors.forename: Wenxiu
authors.initials: W
authors.lastname: Ma
authors.forename: Vanessa
authors.initials: V
authors.lastname: Shiu
authors.forename: Luis A
authors.initials: LA
authors.lastname: Milla
authors.forename: Sangbin
authors.initials: S
authors.lastname: Park
authors.forename: Maria L
authors.initials: ML
authors.lastname: Spletter
authors.forename: Sheng
authors.initials: S
authors.lastname: Tang
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.forename: Xing
authors.initials: X
authors.lastname: Wei
authors.forename: Seung K
authors.initials: SK
authors.lastname: Kim
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Scott
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D050260:Carbohydrate Metabolism; D017124:Conserved Sequence; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology* / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D020869:Gene Expression Profiling; D006458:Hemolymph / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism*; D007814:Larva / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; D007328:Insulin; D012333:RNA, Messenger
keywords: Drosophila; ER; Golgi; RNA-seq; Rab1; Unc-104; insulin; kinesin; laser microdissection; pancreas; transport