A cell-specific functional dissection of the proprotein processing protease amontillado (amon) in Drosophila
Sumners, Caroline O'Neal
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Neuropeptide signals are key regulators of growth, physiology, and development in multicellular organisms that function by binding to membrane-bound receptors initiating intracellular signal transduction networks. Neuropeptides are initially produced as larger inactive precursor molecules that are activated through proteolytic cleavage by proprotein convertases and by other modification events within the secretory pathway. The Drosophila amontillado (amon) gene, which is required for normal growth and development, encodes the homolog of the mammalian proprotein convertase 2 (PC2). This thesis specifically considers amon function in corazonin-producing neuronal cells. Corazonin is an insect neuropeptide associated with ecdysis, the process of larval molting, and with the regulation of glucose levels. Amon mutants show defects in ecdysis and glucose regulation, suggesting that amon may act upstream of corazonin. To determine whether amon is required in corazonin-producing cells for normal growth and development, we reduced amon expression in these cells and evaluated defects in growth, sugar homeostasis, and developmental progression. This group showed longer growth as well as hypoglycemia when compared to wild-type and ablated corazonin cell controls. In a complementary approach, we determined whether amon is sufficient for rescuing normal growth by restoring amon to corazonin-producing cells in an otherwise amon-deficient animal. Expression of amon specifically in this cell set did not rescue animals from amon mutant defects in survival and body length.