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Physiological functioning of preptin and its analogs
Mrázková, Lucie ; Žáková, Lenka (advisor) ; Obšilová, Veronika (referee)
Preptin is a 34 amino acid long peptide that is derived from pro-IGF2, where it is cleaved from its E-domain and produced together with the matured IGF2. In my thesis we prepared two full-length preptins (mouse and human) and 8 preptin analogues (fragments with or without olefin metathesis). The full-length preptins as well as the preptin fragments were synthesized by solid-phase peptide synthesis. Mouse or human preptin served as our reference molecule for comparison with the results of bioassays of preptin analogues. All substances were tested for different biological activities to further elucidate the effect of preptin as a possible biologically active substance. We tested the effect on insulin secretion in pancreatic β-cells, indirectly in- vestigated the effect on bone cell proliferation and tried to approach the discovery of a possible receptor for preptin. From all our results we found that although preptin or some of its analogues have a higher effect than controls, the results are not consistent and the effect is not significantly higher. We were unsuccessful in our search for a receptor, despite having done a number of saturation experiments with radiolabelled preptin in many cell types. We also ruled out at the outset by binding experiments the possibility that preptin is able to bind...
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IGF2 and preptin, biologically active peptides derived from pro-IGF2
Mrázková, Lucie ; Žáková, Lenka (advisor) ; Janovská, Petra (referee)
Pro-IGF2 is a 156 amino acid long protein and it is a prohormone from which two bio- logically active peptides are formed, IGF2 and preptin. IGF2 is an insulin-like growth factor 2 that, together with IGF1 and insulin, shares a similar 3-D structure and similar biological effects. It is a peptide whose sequence corre- sponds to amino acids 1-67 of pro-IGF2. It is produced mainly by the liver, but it is formed in most cells of our body. It is involved in the regulation of growth, differentiation, embryogenesis and in recent years the interest in IGF2 has been increasing mainly due to its function in the central nervous system. Preptin is a newly isolated 34 amino acid long peptide whose sequence corresponds to amino acids 69-102 (E-domain) of pro-IGF2. Preptin affects glucose metabolism as well as bone homeostasis. Disorders in glucose metabolism usually lead to diabetes mellitus, and disorders in bone homeostasis most often lead to osteoporosis. Preptin has been shown to increase the second phase of insulin secretion and to have a positive effect on the proliferation and differentiation of osteoblasts, bone cells promoting bone growth. Keywords: pro-IGF2, preptin, IGF2, E-domain, gene expression, imprinting IGF2
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Preparation of preptin, a peptide secreted from pancreatic islet beta cells, and its effect on insulin secretion
Zrubecká, Denisa ; Žáková, Lenka (advisor) ; Dračínská, Helena (referee)
in English Pancreas is an endocrine tissue which affects many physiological processes in organism. It has been known for a long lime that the pancreatic beta cells secret insulin. However, there are more hormones and substances secreted from the beta cells, mainly peptides such as insulin-like growth factors IGF, shorter peptides like amylin and many more. Some of them have not been even identified. Among these pancreatic products Ch. Buchanan's group from Auckland University, New Zeland identified 34 amino acids long peptide called preptin in 2001. Its amino acid sequence is identical with part of the preform of insulin-like growth factor 2 chain. It has been discovered that preptin has effect on osteoblast proliferation and insulin secretion. Nowadays preptin is being studied like a potential osteoporosis cure thanks to its increasing effect on osteoblasts proliferation. This thesis describes preparation and characterization of human and rat preptin and their two fragments (which contain amino acids 1-16 and 17-34) using solid-phase synthesis. The aim of the thesis is to test effects of rat preptin and its two fragments on insulin secretion in pancreatic beta cell line INS-1E. Part of the thesis is focused on binding assays of human preptin and its two fragments to IGF-1 receptor and also to...
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