MicroRNA miR-7 Regulates Secretion of Insulin-Like Peptides

Area of Science:

• Molecular Biology
• Genetics
• Developmental Biology

Background:

• The insulin/insulin-like growth factor (IGF) pathway links nutrition to growth and metabolism.
• MicroRNAs (miRNAs) are key regulators in biological processes.
• miR-7 is conserved in insulin-producing cells, but its function in regulating insulin-like peptides (ILPs) is unknown.

Purpose of the Study:

• To investigate the conserved functions of miR-7 in regulating ILPs and its impact on growth and metabolism.
• To elucidate the molecular mechanism by which miR-7 influences ILP production and secretion.

Main Methods:

• Utilized Drosophila melanogaster as a model organism.
• Investigated the effects of altered miR-7 levels on ILP availability, body growth, and metabolism.
• Identified and validated direct and indirect targets of miR-7 using genetic knockdown and biochemical assays.
• Examined the conservation of the identified regulatory mechanism in mammalian cells.

Main Results:

• miR-7 limits ILP availability by inhibiting ILP production and secretion in Drosophila.
• Increased miR-7 levels lead to elevated circulating sugars and triglycerides, and decreased animal growth, dependent on ILPs.
• miR-7 directly targets Drosophila F-actin capping protein alpha (CPA), and CPA knockdown mimics miR-7 effects on ILP secretion.
• The mammalian ortholog of CPA (Capza1) is also a direct miR-7 target in mouse β-islet cells.

Conclusions:

• miR-7 regulates insulin signaling and metabolic homeostasis through targeting an actin capping protein.
• This represents a conserved mechanism for an evolutionarily ancient microRNA in regulating insulin.
• The findings highlight a novel pathway for controlling growth and metabolism via miR-7 and actin dynamics.