Publications (45) View all
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Article: Glucagon-like Peptide1 Receptor Mediated Endosomal cAMP Generation Promotes Glucose Stimulated Insulin Secretion in Pancreatic beta Cells.
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ABSTRACT: Glucagon-like peptide 1 (GLP-1) receptor plays a major role in promoting glucose stimulated insulin secretion in pancreatic beta cells. Here in our present study we synthesized a novel functional analogue of GLP-1 conjugated to tetramethyl rhodamine to monitor the internalization of the receptor. Our data shows that receptor after being internalized is sorted to lysosomes. In endosomes, receptor-ligand complex is found to be co-localized with adenylate cyclase. Pharmacological inhibition of endocytosis attenuates GLP-1 receptor mediated cAMP generation and consequent downstream protein kinase-A substrate phosphorylation and glucose stimulated insulin secretion. Our study underlines a paradigm shift in GLP-1 receptor signaling and trafficking. The receptor ligand complex triggers cAMP generation both in plasma membrane and in endosomes which has implications for receptor mediated regulation of insulin secretion.AJP Endocrinology and Metabolism 04/2013; · 4.75 Impact Factor -
Article: Glucagon-like Peptide1 Receptor Mediated Endosomal cAMP Generation Promotes Glucose Stimulated Insulin Secretion in Pancreatic beta Cells
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ABSTRACT: Glucagon-like peptide 1 (GLP-1) receptor plays a major role in promoting glucose stimulated insulin secretion in pancreatic beta cells. Here in our present study we synthesized a novel functional analogue of GLP-1 conjugated to tetramethyl rhodamine to monitor the internalization of the receptor. Our data shows that receptor after being internalized is sorted to lysosomes. In endosomes, receptor-ligand complex is found to be co-localized with adenylate cyclase. Pharmacological inhibition of endocytosis attenuates GLP-1 receptor mediated cAMP generation and consequent downstream protein kinase-A substrate phosphorylation and glucose stimulated insulin secretion. Our study underlines a paradigm shift in GLP-1 receptor signaling and trafficking. The receptor ligand complex triggers cAMP generation both in plasma membrane and in endosomes which has implications for receptor mediated regulation of insulin secretionAJP Endocrinology and Metabolism 04/2013; · 4.75 Impact Factor -
Article: Allosteric inhibition of a zinc-sensing transcriptional repressor: Insights into the arsenic repressor (ArsR) family.
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ABSTRACT: The molecular basis of allosteric regulation remains a subject of intense interest. Staphylococcus aureus CzrA is a member of the ubiquitous arsenic repressor (ArsR) family of bacterial homodimeric metal sensing proteins, and has emerged as a model system for understanding allosteric regulation of operator DNA binding by transition metal ions. Using unnatural amino acid substitution and a standard linkage analysis, we show that a His97' NHε2•••O=C-His67 quaternary structural hydrogen bond is an energetically significant contributor to the magnitude of the allosteric coupling free energy, ∆G(c). A "cavity" introduced just beneath this hydrogen bond in V66A/L68V CzrA results in a dramatic loss of regulation by Zn(II) despite adopting a wild-type global structure and Zn(II) binding and DNA binding affinities only minimally affected from wild-type. The energetics of Zn(II) binding and heterotropic coupling free energies (∆H(c), -T∆S(c)) of the double mutant are also radically altered and suggest that increased internal dynamics leads to poorer allosteric negative regulation in V66A/L68V CzrA. A statistical coupling analysis of 3000 ArsR proteins reveals a sector that links the DNA-binding determinants and the α5 Zn(II) sensing sites through V66/L68 in CzrA. We propose that distinct regulatory sites uniquely characteristic of individual ArsR proteins results from evolution of distinct connectivities to this sector, each capable of driving the same biological outcome, transcriptional derepression.Journal of Molecular Biology 01/2013; · 4.00 Impact Factor -
Article: Outstanding Scientific Achievement Award Lecture 2011: defeating diabesity: the case for personalized combinatorial therapies.
Diabetes 06/2012; 61(6):1309-14. · 8.29 Impact Factor -
Article: Investigation of the Feasibily of an Amide-based Prodrug Under Physiological Conditions
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ABSTRACT: Two different chemical classes of putative amide-based prodrugs of glucagon-like peptide-1 (GLP), one with an amino and the other with α hydroxyl terminal extension have been synthesized and biochemically characterized. The conversion of these terminally-extended peptide hormone analogs to a peptide of much enhanced potency through cyclization of the terminal dipeptide was studied under physiological conditions. The peptides studied demonstrated great stability and little propensity to cyclize to DKP and DMP under physiological conditions. These results stand in contrast to previous reports with model amide-based peptides and indicate that such cleavage is unlikely in larger peptides constituted by naturally coded amino acids.International Journal of Peptide Research and Therapeutics 04/2012; 14(3):255-262. · 0.99 Impact Factor
