Monolysocardiolipin acyltransferase

Monolysocardiolipin acyltransferase (MLCL AT-1) is a mitochondrial acyltransferase that facilitates the remodeling of monolysocardiolipin (MLCL) into cardiolipin.

Trifunctional enzyme subunit alpha, mitochondrial
Identifiers
SymbolHADHA
Alt. symbolsMLCL AT-1
NCBI gene3030
HGNC4801
OMIM600890
RefSeqNP_000173
UniProtP40939
Other data
EC number4.2.1.17
LocusChr. 2 p23.3

History

In 1990, biologists Michael Schlame and Bernd Rustow observed the deacylation of cardiolipin into MLCL, which was then converted back into cardiolipin by a protein using linoleoyl coenzyme A, derived from phosphatidylcholine.[1] However, acyltransferase activities involved in the reacylation of MLCL had not been identified or characterized in any mammalian tissue until 1999, by the Hatch lab at the University of Manitoba, in rat heart mitochondria.[2] In 2003, the same lab purified and characterized an MLCL acyltransferase in pig liver mitochondria,[3] and by comparing this protein against a human protein database, they identified a sequenced but uncharacterized human protein as the enzyme responsible in 2009.[4]

Function

MLCL AT-1 catalyzes the transfer of the fatty acid chain attached to a coenzyme A molecule to an available hydroxyl group on MLCL, producing cardiolipin. This lipid remodeling is separate from the cardiolipin synthesis pathway, and is essential to maintain its unique unsaturated fatty acyl composition. MLCL AT-1 typically utilizes linoleoyl coenzyme A, preferred to oleoyl coenzyme A, which is preferred to palmitoyl coenzyme A.[4]

Activity during apoptosis

MLCL AT-1 activity increases in cells cardiac myoblast cells exposed to 2-deoxyglucose-induced apoptosis.[5] MLCL AT-1 activity also increases in a rat model of spontaneously hypertensive heart failure.[6] Since cardiolipin content is significantly diminished in the inner mitochondrial membrane during apoptosis, the increase of lipid remodeling by MLCL AT-1 may be an effort of the cell to maintain normal cardiolipin levels.

Similarity to mitochondrial trifunctional protein

MLCL AT-1 is completely identical to the 59-kDa C-terminal end of mitochondrial trifunctional protein HADHA, suggesting the possibility that the two proteins may be the product of alternative splicing of the same gene.[4] MLCL AT-1 is likely a splice variant of the alpha subunit of MTP.[7]

Hormone interaction

Treatment with thyroxine, a thyroid hormone, can produce an almost two-fold increase in MLCL AT-1 activity.[8]

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References
  1. Schlame M, Rüstow B (December 1990). "Lysocardiolipin formation and reacylation in isolated rat liver mitochondria". The Biochemical Journal. 272 (3): 589–95. doi:10.1042/bj2720589. PMC 1149749. PMID 2268287.
  2. Ma BJ, Taylor WA, Dolinsky VW, Hatch GM (October 1999). "Acylation of monolysocardiolipin in rat heart". Journal of Lipid Research. 40 (10): 1837–45. PMID 10508203.
  3. Taylor WA, Hatch GM (April 2003). "Purification and characterization of monolysocardiolipin acyltransferase from pig liver mitochondria". The Journal of Biological Chemistry. 278 (15): 12716–21. doi:10.1074/jbc.M210329200. PMID 12569106.
  4. Taylor WA, Hatch GM (October 2009). "Identification of the human mitochondrial linoleoyl-coenzyme A monolysocardiolipin acyltransferase (MLCL AT-1)". The Journal of Biological Chemistry. 284 (44): 30360–71. doi:10.1074/jbc.M109.048322. PMC 2781591. PMID 19737925.
  5. Danos M, Taylor WA, Hatch GM (February 2008). "Mitochondrial monolysocardiolipin acyltransferase is elevated in the surviving population of H9c2 cardiac myoblast cells exposed to 2-deoxyglucose-induced apoptosis". Biochemistry and Cell Biology. 86 (1): 11–20. doi:10.1139/O07-156. PMID 18364741.
  6. Saini-Chohan HK, Holmes MG, Chicco AJ, Taylor WA, Moore RL, McCune SA, Hickson-Bick DL, Hatch GM, Sparagna GC (August 2009). "Cardiolipin biosynthesis and remodeling enzymes are altered during development of heart failure". Journal of Lipid Research. 50 (8): 1600–8. doi:10.1194/jlr.M800561-JLR200. PMC 2724040. PMID 19001357.
  7. Taylor WA, Mejia EM, Mitchell RW, Choy PC, Sparagna GC, Hatch GM (2012). "Human trifunctional protein alpha links cardiolipin remodeling to beta-oxidation". PLOS One. 7 (11): e48628. doi:10.1371/journal.pone.0048628. PMC 3494688. PMID 23152787.
  8. Mutter T, Dolinsky VW, Ma BJ, Taylor WA, Hatch GM (March 2000). "Thyroxine regulation of monolysocardiolipin acyltransferase activity in rat heart". The Biochemical Journal. 346 Pt 2 (2): 403–6. doi:10.1042/0264-6021:3460403. PMC 1220866. PMID 10677359.
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