No abstract

Cardiolipin (CL), the signature phospholipid of mitochondria, is involved in a plethora of cellular processes and is crucial for mitochondrial function and architecture. The de novo synthesis of CL in the mitochondria is followed by a unique remodeling process, in which CL undergoes cycles of deacylation and reacylation. Specific fatty acyl composition is acquired during this process, and remodeled CL contains predominantly unsaturated fatty acids. The importance of CL remodeling is underscored by the life-threatening genetic disorder Barth syndrome (BTHS), caused by mutations in tafazzin, which reacylates monolysocardiolipin (MLCL) generated from the deacylation of CL. Just as CL-deficient yeast mutants have been instrumental in elucidating functions of this lipid, the recently characterized CL-phospholipase mutant cld1Δ and the tafazzin mutant taz1Δ are powerful tools to understand the functions of CL remodeling. In this review, we discuss recent advances in understanding the role of CL in mitochondria with specific focus on the enigmatic functions of CL remodeling.

Cardiolipin (CL), the signature phospholipid of mitochondrial membranes, is crucial for both mitochondrial function and cellular processes outside of the mitochondria. The importance of CL in cardiovascular health is underscored by the life-threatening genetic disorder Barth syndrome (BTHS), which manifests clinically as cardiomyopathy, skeletal myopathy, neutropenia, and growth retardation. BTHS is caused by mutations in the gene encoding tafazzin, the transacylase that carries out the second CL remodeling step. In addition to BTHS, CL is linked to other cardiovascular diseases (CVDs), including cardiomyopathy, atherosclerosis, myocardial ischemia-reperfusion injury, heart failure, and Tangier disease. The link between CL and CVD may possibly be explained by the physiological roles of CL in pathways that are cardioprotective, including mitochondrial bioenergetics, autophagy/mitophagy, and mitogen activated protein kinase (MAPK) pathways. In this review, we focus on the role of CL in the pathogenesis of CVD as well as the molecular mechanisms that may link CL functions to cardiovascular health.

Cardiolipin (CL), the signature phospholipid of mitochondrial membranes, is important for cardiovascular health, and perturbation of CL metabolism is implicated in cardiovascular disease. Although the role of CL in mitochondrial function, biogenesis, and genome stability has been studied, recent findings indicate that it is essential for functions apart from mitochondrial bioenergetics. In this study, we report that mitophagy is perturbed in CL-deficient yeast cells. Mutants of autophagy/mitophagy genes ,, and synthetically interact with CL synthase mutantΔ. CL-deficient cells exhibited decreased GFP-tagged mitochondrial proteins inside the vacuole and decreased free GFP, consistent with decreased mitophagy. Both PKC and high osmolarity glycerol (HOG) MAPK pathways were shown previously to be required for mitophagy. Activation of both MAPKs was defective in CL-deficient cells. Deletion of HOG pathway genes ,, , and exacerbated Δ growth. 1 m sorbitol and 0.2 m NaCl, which induce the HOG pathway, rescued growth of the mutant. Activation of the MAPK Slt2p was defective inΔ cells, and up-regulation of the PKC pathway by expression of the gene, which encodes constitutively activated Pkc1p, rescuedΔ growth and mitophagy defects. These findings indicate that loss of CL impairs MAPK pathway activation, and decreased activation of the PKC pathway leads to defective mitophagy.

BackgroundThe beta-3 adrenergic receptor (β3-AR) Trp64Arg and uncoupling protein 1 (UCP1) -3826 A > G polymorphisms have been reported to be associated with obesity and/or lipid metabolism in some populations. This study examined the possible association of the β3-AR and UCP1 polymorphisms with overweight/obesity or lipid variation in a Southwest Chinese population.MethodsA total of 418 Han Chinese (249 overweight/obese and 169 healthy control subjects) in the Chengdu area were studied using PCR-RFLP analysis. Total serum cholesterol (TC) and triglycerides (TGs) were measured using an enzymatic method. High density lipoprotein cholesterol (HDL-C) was determined after sodium phosphotungstate/magnesium chloride precipitation of low-density lipoproteins by polyvinyl sulfate. Serum apolipoproteins were quantified by radial immunodiffusion.ResultsThe genotype and allele frequencies of the β3-AR Trp64Arg and UCP1 -3826 A > G polymorphisms in overweight/obese subjects exhibited no significant differences compared to the controls. However, subjects carrying the β3-AR TrpTrp genotype and UCP1 AG genotype had higher TG levels than those carrying the Arg allele and AA genotype, respectively (P < 0.05), while controls carrying the β3-AR Arg allele had significantly higher TC and apo AII concentrations than those carrying the TrpTrp genotype (P < 0.05). Additionally, subjects carrying the UCP1 AG genotype exhibited elevated apo C-II and apo C-III levels compared to those carrying the AA genotype (P < 0.05). We were unable to find an association of the UCP1 and β3-AR polymorphisms with low HDL-cholesterolemia in the overweight/obese subjects.ConclusionsThe present study provides evidence that the β3-AR Trp64Arg and UCP1 -3826 A > G polymorphisms are associated with TG levels in overweight/obese Chinese subjects and that the two polymorphisms are also associated with certain lipid and apolipoprotein variations, depending on BMI. However, these polymorphisms are not associated with overweight/obesity or low HDL-cholesterolemia in a Chinese population from the Chengdu area.