The Proline Cycle As a Potential Cancer Therapy Target

Interest in how proline contributes to cancer biology is expanding because of the emerging role of a novel proline metabolic cycle in cancer cell survival, proliferation, and metastasis. Proline biosynthesis and degradation involve the shared intermediate Δ1-pyrroline-5-carboxylate (P5C), which form...

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Bibliographic Details
Published in:Biochemistry (Easton) 2018-06, Vol.57 (25), p.3433-3444
Main Authors: Tanner, John J, Fendt, Sarah-Maria, Becker, Donald F
Format: Article
Language:English
Subjects:
Animals
Biosynthetic Pathways
Cell Proliferation
delta-1-Pyrroline-5-Carboxylate Reductase
Humans
Molecular Docking Simulation
Neoplasms - metabolism
Oxidation-Reduction
Proline - metabolism
Proline Oxidase - metabolism
Pyrroline Carboxylate Reductases - metabolism
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Summary:Interest in how proline contributes to cancer biology is expanding because of the emerging role of a novel proline metabolic cycle in cancer cell survival, proliferation, and metastasis. Proline biosynthesis and degradation involve the shared intermediate Δ1-pyrroline-5-carboxylate (P5C), which forms l-glutamate-γ-semialdehyde (GSAL) in a reversible non-enzymatic reaction. Proline is synthesized from glutamate or ornithine through GSAL/P5C, which is reduced to proline by P5C reductase (PYCR) in a NAD­(P)­H-dependent reaction. The degradation of proline occurs in the mitochondrion and involves two oxidative steps catalyzed by proline dehydrogenase (PRODH) and GSAL dehydrogenase (GSALDH). PRODH is a flavin-dependent enzyme that couples proline oxidation with reduction of membrane-bound quinone, while GSALDH catalyzes the NAD+-dependent oxidation of GSAL to glutamate. PRODH and PYCR form a metabolic relationship known as the proline–P5C cycle, a novel pathway that impacts cellular growth and death pathways. The proline–P5C cycle has been implicated in supporting ATP production, protein and nucleotide synthesis, anaplerosis, and redox homeostasis in cancer cells. This Perspective details the structures and reaction mechanisms of PRODH and PYCR and the role of the proline–P5C cycle in cancer metabolism. A major challenge in the field is to discover inhibitors that specifically target PRODH and PYCR isoforms for use as tools for studying proline metabolism and the functions of the proline–P5C cycle in cancer. These molecular probes could also serve as lead compounds in cancer drug discovery targeting the proline–P5C cycle.
ISSN:0006-2960
1520-4995
DOI:10.1021/acs.biochem.8b00215