Publication Date

2006

Document Type

Dissertation/Thesis

First Advisor

Gasser, Kenneth W.||Mitchell, John L. A.

Degree Name

Ph.D. (Doctor of Philosophy)

Department

Department of Biological Sciences

LCSH

Pancreatic acinar cells--Cytology||Nitric oxide

Abstract

NO signaling is linked to numerous physiological and pathological conditions including apoptosis, angiogenesis, wound repair, reproduction, smooth muscle relaxation, and sarcoplasmic reticulum calcium release. Recently it has been suggested that NO may mediate specific control of cellular signaling and digestive enzyme secretion in pancreatic acinar cells. Thus, the pancreas serves as an excellent model to characterize NO’s divergent effects on signaling components related to secretion. This dissertation provides the first convincing evidence that acinar cells endogenously produce NO via NOS(III), as well as its downstream mediator, cGMP, in response to stimulation with the hormone cholecystokinin (CCK). NO was shown to promote both secretion of digestive enzymes and activation of the ERK-signaling cascade in a cGMPdependent and -independent manner. Furthermore, the results of this dissertation are consistent with the assembly of a complex of proteins that likely modify the efficiency of signal transduction and physiological outcome, rather than a linear cascade with a fixed outcome. CCK and NO were shown to stimulate multiple signaling pathways that culminate in the dynamic assembly of a Ras/ERK signaling complex involving the participation of at least calcium, cGMP, p52Shc, Ras, Raf, Mek, ERK1/2, P13K, PKCa, PKCδ, PKCζ, and NOS(III). Specifically, in the 5 minutes following CCK receptor activation, (1) NO and cGMP are generated, (2) p52Shc is recruited to the complex in a cGMP-, and possibly PKCa-, dependent manner where it is subsequently phosphorylated, (3) NO nitrosylates Ras to enhance GDP/GTP exchange, (4) PKCζ is recruited to the complex, possibly in a P13K-dependent manner where it likely enhances Raf activation, (5) Raf, Mek, and ERK1/2 are maximally phosphorylated, and (6) PKCδ arrives at the complex. Shortly thereafter, (7) NOS(III) dissociates from the complex, possibly via a feedback mechanism involving nitrosyiation, (8) p52Shc dissociates from the complex, and (9) phospho- Raf, -Mek and -ERK1/2 either dissociate from the complex or are dephosphorylated. In conclusion, this dissertation defines several novel roles for NO in pancreatic acinar cell secretion and signal transduction and thus provides a foundation that may be useful for the further characterization of NO signaling dynamics in this and other cell types.

Comments

Includes bibliographical references (pages [130]-149).

Extent

xi, 149, pages (some color pages)

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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