Beck, Megan
(2016)
The regulation and function of long-chain acyl-CoA dehydrogenase and the effect of the single Nucleotide polymorphism K333Q.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Nine acyl-CoA dehydrogenases (ACADs) are involved in mitochondrial fatty acid β-oxidation (FAO), an important energy-producing pathway. Disorders of FAO are common inborn errors of metabolism and genetic deficiencies have been identified for all ACADs except long-chain acyl-CoA dehydrogenase (LCAD). Understanding the function of LCAD and the phenotype of LCAD deficiency may enable identification of unrecognized cases of LCAD deficiency, and eventual treatment, and improve public health.
I hypothesized that human LCAD (hLCAD) and mouse LCAD (mLCAD) are biochemically equivalent, but that hLCAD functions in tissues not normally reliant upon FAO, such as the lung. Additionally, I hypothesized that a missense polymorphism (K333Q), linked to an absence of LCAD antigen in human lung, is deleterious. Recombinant mLCAD, hLCAD, and hLCAD K333Q proteins were purified and biochemically characterized. Recombinant mLCAD was more stable and demonstrated higher catalytic efficiency than hLCAD. Additionally, recombinant hLCAD bearing the K333Q substitution demonstrated lower activity, impaired substrate binding, and reduced stability compared to wild-type hLCAD.
Based on these findings and on western blotting experiments demonstrating higher LCAD expression in human lung than other long-chain ACAD enzymes, I hypothesized that LCAD K333Q may be associated with lung disease. Primary alveolar type II (ATII) cells from individuals homozygous for the minor Q allele had five-fold less LCAD antigen than ATII cells from individuals homozygous for the major K allele, consistent with lower protein stability. Cohorts of neonates with respiratory distress syndrome and children hospitalized for pneumonia were genotyped for LCAD K333Q. Association of lung function with different genotypes at the K333Q locus was examined in the Long Life Family Study (LLFS) (N=4953). Contrary to the hypothesis, the LCAD K333Q locus was not associated with lung disease. Heterozygotes for the Q allele were under-represented among children hospitalized with pneumonia, whereas homozygotes for the K allele were over-represented, suggesting that carrier status for K333Q confers some benefit. Individuals in the LLFS who carried the Q-allele at the K333Q locus had increased lung function. In conclusion, recombinant mLCAD was biochemically superior to hLCAD, which was superior to hLCAD K333Q. However, the K333Q polymorphism was not associated with respiratory distress or pneuomonia-induced complications.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
9 September 2016 |
| Date Type: |
Publication |
| Defense Date: |
3 June 2016 |
| Approval Date: |
9 September 2016 |
| Submission Date: |
24 May 2016 |
| Access Restriction: |
2 year -- Restrict access to University of Pittsburgh for a period of 2 years. |
| Number of Pages: |
114 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
School of Public Health > Human Genetics |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Long-chain acyl-CoA dehydrogenase, Fatty Acid Oxidation, Single Nucleotide Polymorphism K333Q |
| Date Deposited: |
09 Sep 2016 19:33 |
| Last Modified: |
01 Jul 2017 05:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/28080 |
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