Louise Stjerne Knudsen

Structural basis of allosteric ligand-receptor interactions in the insulin/relaxin peptide family: implications for other receptor tyrosine kinases and G-protein-coupled receptors.

The insulin/relaxin superfamily of peptide hormones comprises 10 members in humans. The three members of the insulin‐related subgroup bind to receptor tyrosine kinases (RTKs), while four of the seven members of the relaxin‐like subgroup are now known to bind to G‐protein‐coupled receptors (GPCRs), the so‐called relaxin family peptide receptors (RXFPs). Both systems have a long evolutionary history and play a critical role in fundamental biological processes, such as metabolism, growth, survival and longevity, and reproduction. The structural biology and ligand‐binding kinetics of the insulin and insulin‐like growth factor I receptors have been studied in great detail, culminating in the recent crystal structure of the insulin receptor extracellular domain. Some of the fundamental properties of these receptors, including constitutive dimerization and negative cooperativity, have recently been shown to extend to other RTKs and GPCRs, including RXFPs, confirming kinetic observations made over 30 years ago.

Agonism and Antagonism at the Insulin Receptor

Insulin can trigger metabolic as well as mitogenic effects, the latter being pharmaceutically undesirable. An understanding of the structure/function relationships between insulin receptor (IR) binding and mitogenic/metabolic signalling would greatly facilitate the preclinical development of new insulin analogues. The occurrence of ligand agonism and antagonism is well described for G protein-coupled receptors (GPCRs) and other receptors but in general, with the exception of antibodies, not for receptor tyrosine kinases (RTKs). In the case of the IR, no natural ligand or insulin analogue has been shown to exhibit antagonistic properties, with the exception of a crosslinked insulin dimer (B29-B’29). However, synthetic monomeric or dimeric peptides targeting sites 1 or 2 of the IR were shown to be either agonists or antagonists. We found here that the S961 peptide, previously described to be an IR antagonist, exhibited partial agonistic effects in the 1–10 nM range, showing altogether a bell-shaped dose-response curve. Intriguingly, the agonistic effects of S961 were seen only on mitogenic endpoints (3H-thymidine incorporation), and not on metabolic endpoints (14C-glucose incorporation in adipocytes and muscle cells). The agonistic effects of S961 were observed in 3 independent cell lines, with complete concordance between mitogenicity (3H-thymidine incorporation) and phosphorylation of the IR and Akt. Together with the B29-B’29 crosslinked dimer, S961 is a rare example of a mixed agonist/antagonist for the human IR. A plausible mechanistic explanation based on the bivalent crosslinking model of IR activation is proposed.

Dimerization and Negative Cooperativity in the Relaxin Family Peptide Receptors

Peptides of the relaxin family bind to the relaxin family peptide receptors or RXFPs, members of the G‐protein‐coupled receptor (GPCR) superfamily. For many years, ligand binding to GPCRs was thought to take place as monomeric complexes, ignoring early evidence of negative cooperativity. However, recent research has shown that most GPCRs form constitutive dimers or larger oligomers. The connection between dimerization and negative cooperativity has now been shown for several GPCRs, including the thyroid‐stimulating hormone, luteinizing hormone, and follicle‐stimulating hormone receptors, which like RXFP1 and ‐2 belong to the leucine‐rich repeat‐containing subgroup of class A GPCRs. We recently demonstrated homodimerization and negative cooperativity for RXFP1 and RXFP2 as well as their heterodimerization. Another study showed that RXFP1 has to homodimerize in order to be transported from the endoplasmic reticulum to the cell membrane.

Understanding and scaffolding Danish schoolteachers’ motivation for using classroom-based physical activity: study protocol for a mixed methods study

Introduction The benefits of physical activity for children’s health, both mental and physical, and its positive effects on academic achievement are well established. Research also emphasises that schools could provide a natural setting for regular physical activity. There is, however, a limited amount of knowledge about teachers’ views when it comes to integrating physical activity as part of teaching. The aim of this study is to understand teachers’ motivation for integrating physical activity as part of teaching and to assess their need for guidance and support. Methods and analysis The study uses an explanatory sequential mixed-methods design. Schools from across Denmark are included in the sample. The design comprises two separated phases—a quantitative and qualitative phase. The quantitative phase is guided by the self-determination theory where teachers’ motivation will be measured using the Work Task Motivation Scale for Teachers. The theory of scaffolding guides the qualitative phase, which consists of in-depth interviews with participants selected from the quantitative phase based on levels of motivation and on demographic information. In accordance with the study aims, the analysis of data will identify teachers’ internal and external levels of motivation. The purpose of the qualitative phase is to enhance understanding of teachers’ motivation and of their need for support in the use of physical activity in teaching. Ethics and dissemination All relevant ethics approvals have been acquired. All participants in this study will provide written informed consent prior to data collection. All data emerging from the quantitative and qualitative phase will be anonymised for analysis. Ethics approval was requested from the Regional Committee on Health Research Ethics for Southern Denmark approval ID S-20162000–40 and the Danish Data Protection Agency approval ID 16/15491). The study was deemed not notifiable by both authorities. Trial registration number NCT02894346; Pre-results.