Date of Award

1-1-2009

Document Type

Thesis

Degree Name

M.S.

Department

Biological Sciences

First Advisor

Robert M. Dores, Ph.D.

Second Advisor

Nancy Lorenzon

Third Advisor

Dwight Smith

Keywords

α-MSH, αTC1.9 cells, Endoproteolysis, Fusion protein, Joining peptide, Proopiomelanocortin

Abstract

The maturation process of many prohormone molecules typically requires endoproteolytic cleavage C-terminal of dibasic residues, such as the K141R142↓ site N-terminal of the α-melanocyte stimulating hormone (α-MSH) sequence in Silurana tropicalis proopiomelanocortin (POMC). In order to determine the absolute requirement of basic amino acid residues in the cleavage process, site-directed mutagenesis was employed to substitute alanine for the wild-type residues in the frog POMC open reading frame. Specifically, the following underlined residues were individually targeted for alanine substitution: R 137 Q 138 E 139 N 140 K 141 R 142↓. The mouse pancreatic αTC1.9 cell line, which expresses prohormone convertase 2 (PC2), was selected as the model system for transfection studies. The processing of wild-type frog POMC was correctly predicted to mimic that observed in the intermediate pituitaries of the frog. Moreover, biochemical analysis of mutant frog constructs in the α-cells revealed that alanine substitutions of K141 and R142, but not of R137, disrupted endoproteolytic cleavage resulting in a JP-α-MSH mutant fusion protein. Quantitative real-time PCR analysis of the αTC1.9 cells detected the relative gene expression levels of mouse PC2, glucagon but not PC1/3; detection of S. tropicalis POMC was only evident in the transfected α-cells, which was consistent with immunocytochemical data.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.

Provenance

Received from ProQuest

Rights holder

Quinn Kun Chen

File size

92 p.

File format

application/pdf

Language

en

Discipline

Endocrinology, Neurosciences

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