Identification of the Human Mitochondrial Linoleoyl-coenzyme A Monolysocardiolipin Acyltransferase (MLCL AT-1)

Abstract

Here we report the identification of a previously uncharacterized human protein as the human monolysocardiolipin acyltransferase-1 (MLCL AT-1). Pig liver mitochondria were treated with n-butyl alcohol followed by Q-Sepharose chromatography, preparative gel electrophoresis, cytidine diphosphate-1,2-diacyl-sn-glycerol-Sepharose chromatography, and finally monolysocardiolipin-adriamycin-agarose affinity chromatography. Elution with either monolysocardiolipin or linoleoyl coenzyme A revealed a major band at 74 kDa with high specific activity (2,300 pmol/min/mg) for the acylation of monolysocardiolipin to cardiolipin using Cardiolipin (CL)2 is a major phospholipid found in mammalian mitochondria with a multitude of biological functions (reviewed in Refs. 1-7). For example, CL is responsible for modulation of the activity of several mitochondrial enzymes involved in the generation of ATP (reviewed in Refs. 8, 9). In fact, it has been suggested that CL is the "glue" that holds the mitochondrial respiratory complex together (10). The role of CL in genetic diseases such as Barth syndrome, a rare X-linked genetic disorder, is beginning to emerge. Barth syndrome is the only known genetic disease in which the specific biochemical defect is a reduction in CL and accumulation of monolysocardiolipin (MLCL) caused by mutations in the TAZ gene (reviewed in Refs. 2,7,11,12). In addition, the role that CL plays in apoptosis is now well documented (reviewed in Ref. 13). Thus, maintenance of the appropriate content and fatty acyl composition of CL in mitochondria is essential for proper cellular function.The molecular composition of CL appears to be important for the biological function of CL. In general, there is a selection of a particular kind of fatty acid as well as restriction of the number of fatty acid species (14). The major tetra-acyl molecular species found in rat liver (ϳ57% of total) and bovine heart (ϳ48% of total) are 18:2 in each of the four fatty acyl positions of the cardiolipin molecule. Remodeling of CL is essential to obtain this enrichment of CL with linoleate because CL synthase has no molecular species substrate specificity for cytidine-5Ј-diphosphate-1,2-diacyl-sn-glycerol (15). In addition, the species pattern of CL precursors is similar enough to imply that the enzymes of the CL synthetic pathway are not molecular species-selective (16). Alterations in the molecular composition of CL are associated with various disease states, including diabetes and Barth syndrome (17,18

Dynamic simulation of cardiolipin remodeling: greasing the wheels for an interpretative approach to lipidomics

“…The similarities and differences in acyl selectivity between tissues may result from tissue-specifi c splicing variants or post-translation modifi cations of various known acyltransferases ( 20,38,41,45,52,54 ). Recently, the acyltransferase MLCL AT demonstrated a relative selectivity of 18:2 > 18:1 > 16:1 ( 40 ), which is consistent with the acyl CoA selectivity in the examined heart and liver tissue and also in the examined brain tissue except for 16:1 CoA selectivity.…”

“…The acyl chains utilized for the formation of mature cardiolipin molecular species could originate from a transacylation reaction from PC or PE or via an acyltransferase reaction from acyl CoA (38)(39)(40). To model these selective aspects of the remodeling machinery, we devised an approach that allows for the input of PC and PE sn -2 positional acyl chain composition as well as acyl CoA chain data utilizing designated acyl chain selectivity ( Fig.…”

Acyl-CoA synthetase 1 deficiency alters cardiolipin species and impairs mitochondrial function

“…4 A-C ). To avoid high concentrations of fatty acid, which drives triacylglycerol synthesis, cells were incubated with trace amounts of individual [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C] fatty acids (palmitate, oleate, or linoleate) to measure their incorporation into phospholipids. As measured by ASMs in the media, the oxidation of these fatty acids was 80% lower in the Acsl1 knockdown cells than in controls ( Fig.…”

Myocardial Regulation of Lipidomic Flux by Cardiolipin Synthase

“…Cardiolipin de novo synthesis results in the formation of nascent CL molecular species, which are largely comprised of 16:0-and 18:1-enriched CL molecular species. Nascent CL molecular species are subsequently remodeled by the sequential actions of phospholipase to form monolysocardiolipin followed by reacylation to form mature CL molecular species by remodeling enzymes, such as tafazzin, ALCAT1, or MLCAT (22)(23)(24). Although the molecular species compositions of CL vary between tissues, the predominant mature form of CL in myocardium is tetralinoleic (18:2) CL, which has been implicated in maximizing bioenergetic efficiency (25)(26)(27)(28).…”