Hormonal axes in Drosophila: regulation of hormone release and multiplicity of actions

Abstract

Hormones regulate development, as well as many vital processes in the daily life of an animal. Many of these hormones are peptides that act at a higher hierarchical level in the animal with roles as organizers that globally orchestrate metabolism, physiology and behavior. Peptide hormones can act on multiple peripheral targets and simultaneously convey basal states, such as metabolic status and sleep-awake or arousal across many central neuronal circuits. Thereby, they coordinate responses to changing internal and external environments. The activity of neurosecretory cells is controlled either by (1) cell autonomous sensors, or (2) by other neurons that relay signals from sensors in peripheral tissues and (3) by feedback from target cells. Thus, a hormonal signaling axis commonly comprises several components. In mammals and other vertebrates, several hormonal axes are known, such as the hypothalamic-pituitary-gonad axis or the hypothalamic-pituitary-thyroid axis that regulate reproduction and metabolism, respectively. It has been proposed that the basic organization of such hormonal axes is evolutionarily old and that cellular homologs of the hypothalamic-pituitary system can be found for instance in insects. To obtain an appreciation of the similarities between insect and vertebrate neurosecretory axes, we review the organization of neurosecretory cell systems in Drosophila. Our review outlines the major peptidergic hormonal pathways known in Drosophila and presents a set of schemes of hormonal axes and orchestrating peptidergic systems. The detailed organization of the larval and adult Drosophila neurosecretory systems displays only very basic similarities to those in other arthropods and vertebrates.

Unveiling the sensory and interneuronal pathways of the neuroendocrine connectome inDrosophila

“…the "ring gland connectome") represents the first complete synaptic map of sensory to endocrine pathways in a neuroendocrine system of this complexity, and adds another level of insight on the known humoral functions of the released neuropeptides and hormones. Together with the large amount of knowledge on the function of neurosecretory cells targeting the CC, CA, PG and aorta over the past years (Nässel and Zandawala, 2020), the current analysis increases our understanding of how the neuroendocrine system receives information about external and internal sensory cues. A future challenge in this context is the identification of specific sensory neurons of different origin and modality to define the valence of sensory integration, and the function of the interneurons that enable different pathways to the endocrine organs.…”

Leucokinin and Associated Neuropeptides Regulate Multiple Aspects of Physiology and Behavior in Drosophila

“…Thus, today, we can dissect the functional roles of neuropeptides in single cell types, specific neuronal circuits or in cells of other tissues by a large set of techniques. This has been important in understanding that neuropeptides and peptide hormones are pleiotropic and that their roles can be different at different times in the lifecycle, or at different sites in the brain (see [ 7 , 85 ]).…”

“…A large number of structurally diverse neuropeptides have been identified in insects, and they are known to act on different types of receptors, predominantly G protein-coupled receptors (GPCRs), as co-transmitters, neuromodulators and hormones [ 1 , 2 , 3 , 4 ]. Neuropeptides are major players in regulation of development, growth, reproduction, physiology and behavior and they are, thus, important throughout the lifecycle [ 1 , 2 , 5 , 6 , 7 , 8 , 9 ]. Insects have, for a long time, served in analysis of neuropeptide signaling and endocrinology [ 10 , 11 , 12 ].…”

“…Drosophila has emerged as a versatile model organism in studies of peptide signaling due to the extensive genetic toolbox available, together with access to a huge number of transgene flies from stock centers and the fly community, resources for functional genomics, functional imaging techniques, advances in neuronal connectomics, single-cell transcriptomics and development of efficient physiological and behavioral assays (see, e.g., [ 18 , 19 , 20 , 21 , 22 , 23 , 24 ]). So far, some peptide systems in Drosophila have attracted substantial attention, whereas others are largely neglected (see [ 1 , 5 , 7 , 25 ]). One of the neuropeptides that has gained traction recently in Drosophila is leucokinin (LK).…”

Leucokinin and Associated Neuropeptides Regulate Multiple Aspects of Physiology and Behavior in Drosophila

“…A large number of structurally diverse neuropeptides has been identified in insects and they are known to act on different types of receptors, predominantly GPCRs, as co-transmitters, neuromodulators and hormones [1][2][3][4]. Neuropeptides are major players in regulation of development, growth, reproduction, physiology and behavior and they are thus important throughout the lifecycle [1,2,[5][6][7][8][9]. Insects have for a long time served in analysis of neuropeptide signaling and endocrinology [10][11][12].…”