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Figure 4.1 Drosophila miRNAs in the insulin signalling pathway. The figure summarizes
the functional roles of Drosophila miRNAs involved in the IIS pathway. The functional
interactions of the IIS components are described in the text. miR-14 and nutrient levels
function together in insulin producing neurosecretory cells (NSCs) in the adult Drosophila
brain to regulate Sugarbabe, a zinc finger protein that regulates insulin gene expression
( Varghese et al., 2010 ). miR-278 controls energy homeostasis by regulating its target,
expanded. De-regulation of Expanded in miR-278 mutants results in elevated insulin
production and causes leanness in flies ( Teleman et al., 2006 ). miR-8 activates PI3K by
repressing U-shaped (Ush) in the fat body cells to regulate body size in Drosophila.
U-shaped prevents formation of an active PI3K complex through its direct interaction
with the adapter subunit Dp60 ( Hyunet al., 2009 ). ThemiRNApathway plays an important
role in regulating cell division in the germline stem cells (GSCs) in response to environ-
mental signals. One target that has been shown to mitigate this control is the cyclin-
dependent kinase inhibitor, Dacapo (Dap) ( Hatfield et al., 2005 ). Insulin signaling
regulates expression of Dap in a miRNA dependent manner and multiple miRNAs
(miR-7, mir-278, and miR-309) have been shown to regulate dap 3
UTR ( Yu et al., 2009 ).
Arrows (black) indicate activation and bar-ended lines (red) indicate inhibitory interac-
tions. The IIS pathway components are shown inblue. Broken line indicates an interaction
requiring further study.
'
brain to suppress release of ILPs by the neurosecretory cells ( Geminard,
Rulifson, & Leopold, 2009 ). The fat body amino acid transporter, Slimfast
(Slif ), is an important component in nutritional sensing as knock down of slif
in the fat body causes a non-autonomous reduction in insulin signaling in
other tissues and a reduction in the total body size ( Colombani et al., 2003 ).
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