Type 2 diabetes mellitus is marked by a substantial beta-cell failure which is characterized by defective insulin secretion and resistance to insulin. Understanding the molecular events leading to Glucose-stimulated insulin secretion [GSIS] might serve as therapeutic potential towards diabetes. GSIS involves interplay between small G-proteins and their regulatory factors. Herein, I tested the hypothesis that Arf nucleotide binding site opener [ARNO], a guanine nucleotide exchange factor [GEF] for the small G-protein Arf6, mediates the activation of Arf6, and that ARNO/Arf6 signaling axis, in turn, controls the activation of downstream effectors. Salient features of my study are: [i] ARNO/Arf6 is expressed in clonal β-cells, rodent islets and human islets; [ii] overexpression of inactive mutants of ARNO or Arf6 or siRNAs of Arf6 or ARNO reduces both GSIS and membrane depolarization induced insulin release in clonal β-cell line; [iii] secinH3, a selective inhibitor of ARNO/Arf6 signaling pathway, also inhibits GSIS in INS 832/13 cells and rodent islets; [iv] insulinotropic concentration of glucose stimulates Arf6 activation; [v] glucose-induced Arf6 activation is inhibited by secinH3 or siRNA-ARNO, suggesting a critical involvement of ARNO/Arf6 in insulin secretion; and [vi] glucose promotes association between ARNO and Arf6 as evidenced by co-immunoprecipitation and confocal microscopic studies. These findings provide the first evidence to implicate novel roles for ARNO/Arf6 in insulin secretion.
There are many factors that contribute to GSIS including various enzymes, small G-proteins and actin remodelers. As a step towards elucidating the ARNO/Arf6 signaling cascade, I identified potential downstream effectors that were regulated by ARNO/Arf6 upon glucose stimulation. I identified potential effectors using an ARNO-selective inhibitor [e.g., secinH3] and determined regulatory roles for Arf6/ARNO in promoting phospholipase D [PLD], extracellular-regulated kinases [ERK 1/2], Rac1/Cdc42, NADPH oxidase [Nox], reactive oxygen species [ROS], dynamin-1 and cofilin [actin-severing protein] signaling steps in isolated beta-cells.
Lastly, this work demonstrates dysfunction of Arf6 and Rac1 in beta-cells exposed to glucotoxicity and their abnormal response to physiological concentrations of glucose. This evidence indicates that defective insulin secretion seen in progressive beta-cell failure even after normalization might be at the level of abnormal functioning of small G-proteins. Together my data suggest Arf6/ARNO → PLD →Rac1 → Nox → cofilin signaling cascade regulate the exo-endocytotic pathway leading to GSIS.
","abstract_html":"<p>Type 2 diabetes mellitus is marked by a substantial beta-cell failure which is characterized by defective insulin secretion and resistance to insulin. Understanding the molecular events leading to Glucose-stimulated insulin secretion [GSIS] might serve as therapeutic potential towards diabetes. GSIS involves interplay between small G-proteins and their regulatory factors. Herein, I tested the hypothesis that Arf nucleotide binding site opener [ARNO], a guanine nucleotide exchange factor [GEF] for the small G-protein Arf6, mediates the activation of Arf6, and that ARNO/Arf6 signaling axis, in turn, controls the activation of downstream effectors. Salient features of my study are: [i] ARNO/Arf6 is expressed in clonal β-cells, rodent islets and human islets; [ii] overexpression of inactive mutants of ARNO or Arf6 or siRNAs of Arf6 or ARNO reduces both GSIS and membrane depolarization induced insulin release in clonal β-cell line; [iii] secinH3, a selective inhibitor of ARNO/Arf6 signaling pathway, also inhibits GSIS in INS 832/13 cells and rodent islets; [iv] insulinotropic concentration of glucose stimulates Arf6 activation; [v] glucose-induced Arf6 activation is inhibited by secinH3 or siRNA-ARNO, suggesting a critical involvement of ARNO/Arf6 in insulin secretion; and [vi] glucose promotes association between ARNO and Arf6 as evidenced by co-immunoprecipitation and confocal microscopic studies. These findings provide the first evidence to implicate novel roles for ARNO/Arf6 in insulin secretion.</p> <p>There are many factors that contribute to GSIS including various enzymes, small G-proteins and actin remodelers. As a step towards elucidating the ARNO/Arf6 signaling cascade, I identified potential downstream effectors that were regulated by ARNO/Arf6 upon glucose stimulation. I identified potential effectors using an ARNO-selective inhibitor [e.g., secinH3] and determined regulatory roles for Arf6/ARNO in promoting phospholipase D [PLD], extracellular-regulated kinases [ERK 1/2], Rac1/Cdc42, NADPH oxidase [Nox], reactive oxygen species [ROS], dynamin-1 and cofilin [actin-severing protein] signaling steps in isolated beta-cells. </p> <p>Lastly, this work demonstrates dysfunction of Arf6 and Rac1 in beta-cells exposed to glucotoxicity and their abnormal response to physiological concentrations of glucose. This evidence indicates that defective insulin secretion seen in progressive beta-cell failure even after normalization might be at the level of abnormal functioning of small G-proteins. Together my data suggest Arf6/ARNO → PLD →Rac1 → Nox → cofilin signaling cascade regulate the exo-endocytotic pathway leading to GSIS.</p>","abstract_has_math":false,"creators":["Jayaram, Bhavaani"],"institution":null,"degree_name":"Ph.D.","degree_level":"Open Access Dissertation","degree_discipline":"Pharmaceutical Sciences","degree_department":null,"school":null,"contributors":["ANJANEYULU KOWLURU"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-01-01T08:00:00Z","date_published":"2011-01-01T08:00:00Z","updated_at":"2026-07-24T05:58:57Z","subjects":["ARF6","ARNO","ICMT","INSULIN RELEASE","RAC1","ROS","Medicinal Chemistry and Pharmaceutics","Pharmacology"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://digitalcommons.wayne.edu/oa_dissertations/314","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["ANJANEYULU KOWLURU"]},{"key":"dc:creator","label":"Author","values":["Jayaram, Bhavaani"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2011-01-01T08:00:00Z"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Pharmaceutical Sciences"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Open Access Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["ARF6","ARNO","ICMT","INSULIN RELEASE","RAC1","ROS","Medicinal Chemistry and Pharmaceutics","Pharmacology"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://digitalcommons.wayne.edu/oa_dissertations/314"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Type 2 diabetes mellitus is marked by a substantial beta-cell failure which is characterized by defective insulin secretion and resistance to insulin. Understanding the molecular events leading to Glucose-stimulated insulin secretion [GSIS] might serve as therapeutic potential towards diabetes. GSIS involves interplay between small G-proteins and their regulatory factors. Herein, I tested the hypothesis that Arf nucleotide binding site opener [ARNO], a guanine nucleotide exchange factor [GEF] for the small G-protein Arf6, mediates the activation of Arf6, and that ARNO/Arf6 signaling axis, in turn, controls the activation of downstream effectors. Salient features of my study are: [i] ARNO/Arf6 is expressed in clonal β-cells, rodent islets and human islets; [ii] overexpression of inactive mutants of ARNO or Arf6 or siRNAs of Arf6 or ARNO reduces both GSIS and membrane depolarization induced insulin release in clonal β-cell line; [iii] secinH3, a selective inhibitor of ARNO/Arf6 signaling pathway, also inhibits GSIS in INS 832/13 cells and rodent islets; [iv] insulinotropic concentration of glucose stimulates Arf6 activation; [v] glucose-induced Arf6 activation is inhibited by secinH3 or siRNA-ARNO, suggesting a critical involvement of ARNO/Arf6 in insulin secretion; and [vi] glucose promotes association between ARNO and Arf6 as evidenced by co-immunoprecipitation and confocal microscopic studies. These findings provide the first evidence to implicate novel roles for ARNO/Arf6 in insulin secretion.
There are many factors that contribute to GSIS including various enzymes, small G-proteins and actin remodelers. As a step towards elucidating the ARNO/Arf6 signaling cascade, I identified potential downstream effectors that were regulated by ARNO/Arf6 upon glucose stimulation. I identified potential effectors using an ARNO-selective inhibitor [e.g., secinH3] and determined regulatory roles for Arf6/ARNO in promoting phospholipase D [PLD], extracellular-regulated kinases [ERK 1/2], Rac1/Cdc42, NADPH oxidase [Nox], reactive oxygen species [ROS], dynamin-1 and cofilin [actin-severing protein] signaling steps in isolated beta-cells.
Lastly, this work demonstrates dysfunction of Arf6 and Rac1 in beta-cells exposed to glucotoxicity and their abnormal response to physiological concentrations of glucose. This evidence indicates that defective insulin secretion seen in progressive beta-cell failure even after normalization might be at the level of abnormal functioning of small G-proteins. Together my data suggest Arf6/ARNO → PLD →Rac1 → Nox → cofilin signaling cascade regulate the exo-endocytotic pathway leading to GSIS.
"]},{"key":"dc:title","label":"Title","values":["Small gtp-binding proteins in insulin secretion"]}]}],"canonical_facts":{"dc:contributor":["ANJANEYULU KOWLURU"],"dc:creator":["Jayaram, Bhavaani"],"dc:date.available":["2011-01-01T08:00:00Z"],"dc:description.abstract":["Type 2 diabetes mellitus is marked by a substantial beta-cell failure which is characterized by defective insulin secretion and resistance to insulin. Understanding the molecular events leading to Glucose-stimulated insulin secretion [GSIS] might serve as therapeutic potential towards diabetes. GSIS involves interplay between small G-proteins and their regulatory factors. Herein, I tested the hypothesis that Arf nucleotide binding site opener [ARNO], a guanine nucleotide exchange factor [GEF] for the small G-protein Arf6, mediates the activation of Arf6, and that ARNO/Arf6 signaling axis, in turn, controls the activation of downstream effectors. Salient features of my study are: [i] ARNO/Arf6 is expressed in clonal β-cells, rodent islets and human islets; [ii] overexpression of inactive mutants of ARNO or Arf6 or siRNAs of Arf6 or ARNO reduces both GSIS and membrane depolarization induced insulin release in clonal β-cell line; [iii] secinH3, a selective inhibitor of ARNO/Arf6 signaling pathway, also inhibits GSIS in INS 832/13 cells and rodent islets; [iv] insulinotropic concentration of glucose stimulates Arf6 activation; [v] glucose-induced Arf6 activation is inhibited by secinH3 or siRNA-ARNO, suggesting a critical involvement of ARNO/Arf6 in insulin secretion; and [vi] glucose promotes association between ARNO and Arf6 as evidenced by co-immunoprecipitation and confocal microscopic studies. These findings provide the first evidence to implicate novel roles for ARNO/Arf6 in insulin secretion.
There are many factors that contribute to GSIS including various enzymes, small G-proteins and actin remodelers. As a step towards elucidating the ARNO/Arf6 signaling cascade, I identified potential downstream effectors that were regulated by ARNO/Arf6 upon glucose stimulation. I identified potential effectors using an ARNO-selective inhibitor [e.g., secinH3] and determined regulatory roles for Arf6/ARNO in promoting phospholipase D [PLD], extracellular-regulated kinases [ERK 1/2], Rac1/Cdc42, NADPH oxidase [Nox], reactive oxygen species [ROS], dynamin-1 and cofilin [actin-severing protein] signaling steps in isolated beta-cells.
Lastly, this work demonstrates dysfunction of Arf6 and Rac1 in beta-cells exposed to glucotoxicity and their abnormal response to physiological concentrations of glucose. This evidence indicates that defective insulin secretion seen in progressive beta-cell failure even after normalization might be at the level of abnormal functioning of small G-proteins. Together my data suggest Arf6/ARNO → PLD →Rac1 → Nox → cofilin signaling cascade regulate the exo-endocytotic pathway leading to GSIS.
"],"dc:identifier":["https://digitalcommons.wayne.edu/oa_dissertations/314"],"dc:subject":["ARF6","ARNO","ICMT","INSULIN RELEASE","RAC1","ROS","Medicinal Chemistry and Pharmaceutics","Pharmacology"],"dc:title":["Small gtp-binding proteins in insulin secretion"],"thesis:degree_discipline":["Pharmaceutical Sciences"],"thesis:degree_level":["Open Access Dissertation"],"thesis:degree_name":["Ph.D."]},"updated_at":"2026-07-24T05:58:57Z"}