C-terminal Modifications and Short Oligopeptide Mimetics of Pancreatic Polypeptides in Y4 Receptor Activation

Abstract

Pancreatic polypeptide (PP) is a gut-derived hormone of the neuropeptide Y family that regulates appetite, gastrointestinal motility, and energy homeostasis through activation of the neuropeptide Y4 receptor (Y4R). With the rising prevalence of obesity, understanding the molecular pharmacology and structure-function relationships of PP-Y4R interactions is essential for the development of novel anti-obesity therapies.

In this thesis, Y4 receptor activation was investigated using pharmacokinetically enhanced PP analogues, C-terminally modified peptides, short oligopeptide mimetics, and a synthetic small-molecule ligand. Functional signaling was assessed in Cos7 cells expressing Y4R using BRET-based cAMP inhibition and IP3 accumulation assays.

The results demonstrate that removal of the DPP-4 cleavage site and lipidation at either the N-terminus or position 13 do not impair Y4R activation, supporting strategies to enhance PP stability without loss of function. C-terminal modifications of PP showed that the Tyr36 side chain is essential for Y4 receptor activation, whereas the C-terminal carboxamide is not, as loss of Tyr36 reduced potency or caused complete loss of function. Short oligopeptide mimetics activated Y4R mainly as low-potency partial agonists; peptides with tryptophan at position 34 showed the lowest potency, and one displayed partial antagonistic behavior, indicating that C-terminal substitutions can shift Y4R signaling away from agonism. The small-molecule compound (S)-VU0637120 markedly reduced PP potency and efficacy, suggesting it acts as a competitive antagonist.

Overall, this work provides structure-activity insights into Y4R activation and identifies key molecular determinants governing potency and efficacy, supporting the design of Y4R-targeted therapeutics for metabolic disorders.

Popular Abstract

New Molecular Insights for Developing Drugs Against Obesity and Overweight

Energy balance is crucial for human health. When this balance is disrupted, it can lead to obesity, a health condition that is increasing globally and is often associated with other diseases. This thesis investigates a new, promising drug that can influence appetite and satiety.

Energy balance refers to the relationship between the energy we get from food and the energy the body spends, for example, through metabolism and physical activity. When this balance is disturbed over a long period, it can lead to overweight and, in more severe cases, obesity. Today, obesity is a growing societal problem and is often associated with other diseases, such as cardiovascular disease, liver disease, and type 2 diabetes. Previously, the focus has mainly been on lifestyle changes such as diet and exercise. However, new research and drugs, such as Ozempic, have shown that it is possible to regulate appetite and feelings of fullness through drug treatment. This master’s thesis examines a promising drug candidate against obesity and overweight, based on the body’s own signaling system.

In the body, there is a natural hormone secreted by the pancreas called pancreatic polypeptide (PP). The body is regulated by an advanced signaling system where different molecules, called ligands, bind to receptors, similar to a key fitting into a lock. PP is the natural ligand for the Y4 receptor, and together they regulate appetite, food intake, how quickly food passes through the gut, and the body’s energy balance. For a substance to work as a drug, it must have several properties. It needs to be active in the body for a long time without breaking down too quickly, while also being small enough to be formulated into an effective drug, ideally one that can be taken orally. Additionally, the molecule must bind to its receptor correctly and produce the desired effect.

In this work, the study focused on how PP can be modified to meet these requirements. By altering the peptide’s structure, such as by adding lipids and removing parts that are easily broken down by enzymes, PP could be made longer-acting. Often, such modifications can reduce receptor activation, but the results here showed that PP could still activate the Y4 receptor normally, which is very promising for drug development. The work also focused on making the peptide smaller. Therefore, the C-terminal, the part of PP that binds directly to the receptor (like the tip of a key that goes into a lock, while the rest of the molecule functions as the handle), was studied. The short C-terminal peptides were able to bind and activate the receptor using only the last four amino acids. At the same time, variants were identified that instead blocked the receptor and reduced its activity, which could be important for controlling receptor function in different ways.

We still know surprisingly little about how PP and the Y4 receptor actually work together at the molecular level, even though this interaction is important. This project zooms in on the details and shows which parts of PP really do the job. That knowledge can guide future studies, smarter animal experiments, and, in the long run, new treatments for obesity and other metabolic disorders.

• author: Silva, Annika
• supervisor: Johan Svensson Bonde; Thue Schwartz; Jacob Peterson
• organization: Pure and Applied Biochemistry; Computational Chemistry
• course: KBKM05 20252
• year: 2026
• type: H2 - Master's Degree (Two Years)
• subject: Medicine and Health Sciences
• keywords: Obesity, Pancreatic polypeptide, Neuropeptide Y 4 Receptor, Molecular Pharmacology, Applied Biochemistry
• language: English
• id: 9222609
• date added to LUP: 2026-02-16 09:48:32
• date last changed: 2026-02-16 09:48:32