The human genome encodes 10 insulin-like genes, whereas the genome remarkably encodes 40 insulin-like genes. Knockout strategies to determine the roles of all the insulin/insulin-like peptide ligands (INS) in has been challenging due to functional redundancy. Here, we individually overexpressed each of the 40 genes pan-neuronally, and monitored multiple phenotypes including: L1 arrest life span, neuroblast divisions under L1 arrest, dauer formation, and fat accumulation, as readouts to characterize the functions of each INS Of the 40 INS peptides, we found functions for 35 INS peptides and functionally categorized each as agonists, antagonists, or of pleiotropic function. In particular, we found that 9 of 16 agonistic INS peptides shortened L1 arrest life span and promoted neuroblast divisions during L1 arrest. Our study revealed that a subset of β-class INS peptides that contain a distinct F peptide sequence are agonists. Our work is the first to categorize the structures of INS peptides and relate these structures to the functions of all 40 INS peptides Our findings will promote the study of insulin function on development, metabolism, and aging-related diseases.

Movement inCaenorhabditis elegans is the result of sensory cues creating stimulatory and inhibitory output from sensory neurons. Four interneurons (AIA, AIB, AIY, and AIZ) are the primary recipients of this information that is further processed en route to motor neurons and muscle contraction. C. elegans has >1,000 G proteincoupled receptors (GPCRs), and their contribution to sensory-based movement is largely undefined. We show that an allatostatin/ galanin-like GPCR (NPR-9) is found exclusively in the paired AIB interneuron. AIB interneurons are associated with local search/ pivoting behavior. npr-9 mutants display an increased local search/ pivoting that impairs their ability to roam and travel long distances on food. With impaired roaming behavior on food npr-9 mutants accumulate more intestinal fat as compared with wild type. Overexpression of NPR-9 resulted in a gain-of-function phenotype that exhibits enhanced forward movement with lost pivoting behavior off food. As such the animal travels a great distance off food, creating arcs to return to food. These findings indicate that NPR-9 has inhibitory effects on the AIB interneuron to regulate foraging behavior, which, in turn, may affect metabolic rate and lipid storage.neuropeptide receptor ͉ nerve transmission ͉ foraging ͉ glutamate receptor ͉ interneuron A major challenge in neurobiology is to understand the control of behavior at the molecular level. Neuropeptides and their receptors offer promising candidates for the regulation of various behaviors and changes in physiology. The Caenorhabditis elegans genome sequence has allowed the identification of 109 putative neuropeptide genes encoding precursors that may be processed to Ϸ250 neuropeptides (1-3). These neuropeptides are grouped into three families: FMRFamide-related peptides (f lp), insulin-like peptides (ins), and neuropeptide-like-peptides (nlps). C. elegans expresses Ͼ1,000 orphan G protein-coupled receptors (GPCRs). More than 50 GPCRs resemble known receptors for known neuropeptide families based on phylogenetic comparisons with known vertebrate GPCRs (4). Of these GPCRs, based on sequence identity, C. elegans gene ZK455.3 expresses an nlp receptor, NPR-9, that is most similar to insect allatostatin/ mammalian galanin receptors (5-8). Allatostatins are a family of neuropeptides that share a conserved C-terminal sequence -Tyr/PheXaaPheGlyLeu-NH 2 and are widespread throughout the invertebrate lineage (9, 10). In insects, allatostatins regulate numerous physiological functions, including inhibition of juvenile hormone biosynthesis (11, 12), inhibition of muscle contraction (13), myoendocrine regulation (14, 15), neuromodulation (16), and regulation of enzymatic activities (17) and ecdysis (18). Similarly, mammalian galanin modulates a wide variety of processes that range from neurotransmission, nociception, feeding and metabolism, energy and osmotic homeostasis and learning and memory (19). We report that NPR-9 is uniquely localized in interneuron AIB to negatively regulate a variety of inputs th...

Insulin and insulin-like growth factor-1 signaling have fundamental roles in energy metabolism, growth and development. Recent research suggests hyperactive insulin receptor (IR) and hyperinsulinemia are cancer risk factors. However, the mechanisms that account for the link between the hyperactive insulin signaling and cancer risk are not well understood. Here we show that an insulin-like signaling inhibits the DAF-18/(phosphatase and tensin homolog) PTEN tumour suppressor in Caenorhabditis elegans and that this regulation is conserved in human breast cancer cells. We show that inhibiting the IR increases PTEN protein levels, while increasing insulin signaling decreases PTEN protein levels. Our results show that the kinase region of IRb subunit physically binds to PTEN and phosphorylates on Y27 and Y174. Our genetic results also show that DAF-2/IR negatively regulates DAF-18/PTEN during C. elegans axon guidance. As PTEN is an important tumour suppressor, our results therefore suggest a possible mechanism for increased cancer risk observed in hyperinsulinemia and hyperactive IR individuals.

The human genome encodes ten insulin-like genes, whereas the C. elegans genome remarkably encodes forty insulin-like genes. The roles of insulin/insulin-like peptide ligands (INS) in C. elegans are not well understood. The functional redundancy of the forty INS genes makes it challenging to address their functions by using knock out strategies. Here, we individually overexpressed each of the forty ins genes pan-neuronally, and monitored multiple phenotypes including: L1 arrest life span, neuroblast divisions under L1 arrest, dauer formation and fat accumulation, as readouts to characterize the functions of each INS in vivo. Of the 40 INS peptides, we found functions for 35 INS peptides and functionally categorized each as agonists, antagonists or of pleiotropic function. In particular, we found that 9 of 16 agonistic INS peptides shortened L1 arrest life span and promoted neuroblast divisions during L1 arrest. Our study revealed that a subset of β-class INS peptides that contain a distinct F peptide sequence are agonists. Our work is the first to categorize the structures of INS peptides and relate these structures to the functions of all forty INS peptides in vivo. Our findings will promote the study of insulin function on development, metabolism, and aging-related diseases.Author SummaryInsulin and insulin-like growth factors are found in all animals and regulate many physiological and developmental processes. The human genome has 10 insulin-like peptides including the well characterized insulin hormone. The nematode C. elegans has 40 insulin-like (INS) peptide genes. All 40 INS peptides have been knocked out but no single INS gene knock out resembles the loss of the C. elegans insulin receptor suggesting that the other INS peptides can compensate when one INS is lost. We have used a genetic approach to overexpress each of the 40 INS peptides in C. elegans and have identified in vivo function for 35 of the 40 INS peptides. Like the human insulin and IGF-1, C. elegans INS peptides are derived from a precursor protein and we have shown that INS peptides with an associated peptide called the F peptide are strong activators of the C. elegans insulin-like receptor. We also identified several INS peptides that inhibit the insulin-like receptor and these inhibitory INS peptides may have therapeutic potential.