A Single Mutation in the Nonamyloidogenic Region of Islet Amyloid Polypeptide Greatly Reduces Toxicity Export

@article{citeulike:3494675, abstract = {Abstract: Islet amyloid polypeptide (IAPP or amylin) is a 37-residue peptide secreted with insulin by ²-cells in the islets of Langerhans. The aggregation of the peptide into either amyloid fibers or small soluble oligomers has been implicated in the death of ²-cells during type 2 diabetes through disruption of the cellular membrane. The actual form of the peptide responsible for ²-cell death has been a subject of controversy. Previous research has indicated that the N-terminal region of the peptide (residues 119) is primarily responsible for the membrane-disrupting effect of the hIAPP peptide and induces membrane disruption to a similar extent as the full-length peptide without forming amyloid fibers when bound to the membrane. The rat version of the peptide, which is both noncytotoxic and nonamyloidogenic, differs from the human peptide by only one amino acid residue: Arg18 in the rat version while His18 in the human version. To elucidate the effect of this difference, we have measured in this study the effects of the rat and human versions of IAPP119 on islet cells and model membranes. Fluorescence microscopy shows a rapid increase in intracellular calcium levels of islet cells after the addition of hIAPP119, indicating disruption of the cellular membrane, while the rat version of the IAPP119 peptide is significantly less effective. Circular dichroism experiments and dye leakage assays on model liposomes show that rIAPP119 is deficient in binding to and disrupting lipid membranes at low but not at high peptide to lipid ratios, indicating that the ability of rIAPP119 to form small aggregates necessary for membrane binding and disruption is significantly less than hIAPP119. At pH 6.0, where H18 is likely to be protonated, hIAPP119 resembles rIAPP119 in its ability to cause membrane disruption. Differential scanning calorimetry suggests a different mode of binding to the membrane for rIAPP119 compared to hIAPP119. Human IAPP119 has a minimal effect on the phase transition of lipid vesicles, suggesting a membrane orientation of the peptide in which the mobility of the acyl chains of the membrane is relatively unaffected. Rat IAPP119, however, has a strong effect on the phase transition of lipid vesicles at low concentrations, suggesting that the peptide does not easily insert into the membrane after binding to the surface. Our results indicate that the modulation of the peptide orientation in the membrane by His18 plays a key role in the toxicity of nonamyloidogenic forms of hIAPP.}, address = {Departments of Chemistry and Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055}, author = {Brender, Jeffrey R. and Hartman, Kevin and Reid, Kendra R. and Kennedy, Robert T. and Ramamoorthy, Ayyalusamy}, citeulike-article-id = {3494675}, citeulike-linkout-0 = {http://dx.doi.org/10.1021/bi801427c}, citeulike-linkout-1 = {http://pubs.acs.org/doi/abs/10.1021/bi801427c}, day = {7}, doi = {10.1021/bi801427c}, journal = {Biochemistry}, keywords = {amiloid, brend08pdf, islet, peptide}, month = {November}, posted-at = {2008-11-07 23:09:21}, priority = {2}, title = {A Single Mutation in the Nonamyloidogenic Region of Islet Amyloid Polypeptide Greatly Reduces Toxicity}, url = {http://dx.doi.org/10.1021/bi801427c}, year = {2008} }

TY - JOUR ID - citeulike:3494675 L3 - citeulike-article-id:3494675 N2 - Abstract: Islet amyloid polypeptide (IAPP or amylin) is a 37-residue peptide secreted with insulin by ²-cells in the islets of Langerhans. The aggregation of the peptide into either amyloid fibers or small soluble oligomers has been implicated in the death of ²-cells during type 2 diabetes through disruption of the cellular membrane. The actual form of the peptide responsible for ²-cell death has been a subject of controversy. Previous research has indicated that the N-terminal region of the peptide (residues 119) is primarily responsible for the membrane-disrupting effect of the hIAPP peptide and induces membrane disruption to a similar extent as the full-length peptide without forming amyloid fibers when bound to the membrane. The rat version of the peptide, which is both noncytotoxic and nonamyloidogenic, differs from the human peptide by only one amino acid residue: Arg18 in the rat version while His18 in the human version. To elucidate the effect of this difference, we have measured in this study the effects of the rat and human versions of IAPP119 on islet cells and model membranes. Fluorescence microscopy shows a rapid increase in intracellular calcium levels of islet cells after the addition of hIAPP119, indicating disruption of the cellular membrane, while the rat version of the IAPP119 peptide is significantly less effective. Circular dichroism experiments and dye leakage assays on model liposomes show that rIAPP119 is deficient in binding to and disrupting lipid membranes at low but not at high peptide to lipid ratios, indicating that the ability of rIAPP119 to form small aggregates necessary for membrane binding and disruption is significantly less than hIAPP119. At pH 6.0, where H18 is likely to be protonated, hIAPP119 resembles rIAPP119 in its ability to cause membrane disruption. Differential scanning calorimetry suggests a different mode of binding to the membrane for rIAPP119 compared to hIAPP119. Human IAPP119 has a minimal effect on the phase transition of lipid vesicles, suggesting a membrane orientation of the peptide in which the mobility of the acyl chains of the membrane is relatively unaffected. Rat IAPP119, however, has a strong effect on the phase transition of lipid vesicles at low concentrations, suggesting that the peptide does not easily insert into the membrane after binding to the surface. Our results indicate that the modulation of the peptide orientation in the membrane by His18 plays a key role in the toxicity of nonamyloidogenic forms of hIAPP. JF - Biochemistry AD - Departments of Chemistry and Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055 TI - A Single Mutation in the Nonamyloidogenic Region of Islet Amyloid Polypeptide Greatly Reduces Toxicity KW - amiloid KW - brend08pdf KW - islet KW - peptide AU - Brender, Jeffrey AU - Hartman, Kevin AU - Reid, Kendra AU - Kennedy, Robert AU - Ramamoorthy, Ayyalusamy PY - 2008/11/07/ UR - http://dx.doi.org/10.1021/bi801427c ER -