The Structural Requirements of Gastrin and Glycine-Extended Gastrin for Binding to Receptors from Normal and Cancerous Human Tissues
type: CreativeWork
description: Structural requirements for binding of gastrin to the human CCK2 receptor and the existence of receptors for gastrin peptides on human colon cancer cells were investigated. CCK2 receptor studies focused on the importance of the C-terminal Phe and putative P- tum region of gastrin 17 (G17). Gastrin analogs were synthesized in which either Phe at position 17 was removed or replaced with various amino acids or Gly at position 13 was replaced with constrained amino acids. Binding of the peptides to CHO cell membranes expressing the human CCK2 receptor was assessed in competition with [3H]CCK8. The biological activity of peptides that competed with ['HJCCK8 was determined by their ability to stimulate guanine nucleotide exchange on CHO cell membranes. The secondary structure of peptides modified at position 13 was investigated using MD, ECD Spectroscopy, and VCD Spectroscopy.|The role of gastrin peptides in colon cancer was investigated using the human colon cancer cell lines DLD-1 and HT-29. Binding of CCK8 and gastrin peptides to membrane preparations and whole cells, in competition with [3H][Leul5]G17-Gly and [l0I][Leu‘5]G17-Gly, was assessed. Binding of ['HJCCK8 to DLD-1 membranes was also examined. The ability of peptides to stimulate the growth of the cancer cells was determined by cell counting.|Removal of Phe at position 17 of G17 resulted in complete loss of binding to the human CCK.2 receptor. A side chain larger than Leu is required for binding but aromaticity is not important. Additionally, neither the size nor the electron withdrawing/donating properties of the para-substituent of Phe affected binding. Altering side chain or backbone orientation either by side chain constraint or D-amino acid substitution results in a marked decrease in binding. The binding affinity is strongly correlated with the biological activity of each analog, demonstrating little role for the residue at position 17 in receptor activation. Based on these results, the use of des-Phe ana…
abstract: Structural requirements for binding of gastrin to the human CCK2 receptor and the existence of receptors for gastrin peptides on human colon cancer cells were investigated. CCK2 receptor studies focused on the importance of the C-terminal Phe and putative P- tum region of gastrin 17 (G17). Gastrin analogs were synthesized in which either Phe at position 17 was removed or replaced with various amino acids or Gly at position 13 was replaced with constrained amino acids. Binding of the peptides to CHO cell membranes expressing the human CCK2 receptor was assessed in competition with [3H]CCK8. The biological activity of peptides that competed with ['HJCCK8 was determined by their ability to stimulate guanine nucleotide exchange on CHO cell membranes. The secondary structure of peptides modified at position 13 was investigated using MD, ECD Spectroscopy, and VCD Spectroscopy.|The role of gastrin peptides in colon cancer was investigated using the human colon cancer cell lines DLD-1 and HT-29. Binding of CCK8 and gastrin peptides to membrane preparations and whole cells, in competition with [3H][Leul5]G17-Gly and [l0I][Leu‘5]G17-Gly, was assessed. Binding of ['HJCCK8 to DLD-1 membranes was also examined. The ability of peptides to stimulate the growth of the cancer cells was determined by cell counting.|Removal of Phe at position 17 of G17 resulted in complete loss of binding to the human CCK.2 receptor. A side chain larger than Leu is required for binding but aromaticity is not important. Additionally, neither the size nor the electron withdrawing/donating properties of the para-substituent of Phe affected binding. Altering side chain or backbone orientation either by side chain constraint or D-amino acid substitution results in a marked decrease in binding. The binding affinity is strongly correlated with the biological activity of each analog, demonstrating little role for the residue at position 17 in receptor activation. Based on these results, the use of des-Phe ana…
author: Ahmed, Shawn
language: en_US
date published: 2004-05-13
date modified: 2026-07-24T01:50:24Z
provider: Creighton University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Creighton University

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property ID: Handle
value: http://hdl.handle.net/10504/65275