Item – Theses Canada

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OCLC number
32013134
Author
Wong, Margaret,1961-
Title
The role of cAMP-dependent protein kinase in the regulation of steroidogenesis in Y1 mouse adrenocortical tumor cells.
Degree
Ph. D. -- University of Toronto, 1993
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, 1994.
Description
3 microfiches.
Notes
University Microfilms order no. UMI00459685.
Includes bibliographical references.
Abstract
The protein kinase-defective Y1 mutants, Kin-7 and Kin-8 expressed a structurally defective regulatory subunit (R1) of the type I cAMP-dependent protein kinase. The mutant RI had reduced ability to bind cAMP and consequently, cAMP-dependent protein kinase (cAMPdPK) activity in the mutants was impaired. The two Kin mutants also were resistant to ACTH- and cAMP-regulated steroidogenesis, cell growth and morphology. To examine the causal relationship between the mutations in cAMPdPK and the resistance to ACTH and cAMP, the Kin mutants were transfected with expression vectors encoding wild-type cAMPdPK subunits. Kin-7 and Kin-8 cells recovered cAMPdPK activity when transfected with expression vectors encoding mouse wild-type regulatory and catalytic subunits respectively. The recovery of cAMPdPK activity was accompanied by the recovery of steroidogenic and morphological responses to ACTH and cAMP, suggesting an obligatory role for cAMPdPK in the regulation of these cellular responses. The growth inhibitory effects of cAMP, however, were not recovered in Kin-8 cells transfected with the catalytic subunit of the enzyme, suggesting that the resistance to cAMP-regulated growth inhibition may have resulted from second-site mutations in the original Kin-8 cells or in the transformants. The RI mutations in the Kin clones impaired basal and cAMP-stimulated expression of transcripts encoding the side chain cleavage and 11$\beta$-hydroxylase cytochrome P450 enzymes, suggesting that a functional cAMPdPK may be required in the expression and the maintenance of the levels of these steroidogenic enzymes. In addition, the Kin mutations also impaired the mobilization of the substrate cholesterol, suggesting that cAMPdPK was involved in the regulation of steroidogenesis at multiple sites.
ISBN
0315863927
9780315863927