Cardiolipin Regulates Mitophagy through the Protein Kinase C Pathway.

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 ATG8, ATG18, and ATG32 synthetically interact with CL synthase mutant crd1Δ. 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 SHO1, SSK1, STE50, and HOG1 exacerbated crd1Δ 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 in crd1Δ cells, and up-regulation of the PKC pathway by expression of the PKC1R398P gene, which encodes constitutively activated Pkc1p, rescued crd1Δ 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.

Cardiolipin remodeling: a regulatory hub for modulating cardiolipin metabolism and function.

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.

The Role of Cardiolipin in Cardiovascular Health.

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.

Effect of the beta-3 adrenergic receptor Trp64Arg and uncoupling protein 1-3826 A>G genotypes on lipid and apolipoprotein levels in overweight/obese and non-obese Chinese subjects.

BACKGROUND: The beta-3 adrenergic receptor (ß3-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 ß3-AR and UCP1 polymorphisms with overweight/obesity or lipid variation in a Southwest Chinese population. METHODS: A 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. RESULTS: The genotype and allele frequencies of the ß3-AR Trp64Arg and UCP1 -3826 A>G polymorphisms in overweight/obese subjects exhibited no significant differences compared to the controls. However, subjects carrying the ß3-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 ß3-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 ß3-AR polymorphisms with low HDL-cholesterolemia in the overweight/obese subjects. CONCLUSIONS: The present study provides evidence that the ß3-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.

[Analysis of -3826A/G polymorphism in the promoter of the uncoupling protein-1 gene in Chinese non-obese and obese populations].

OBJECTIVE: To investigate the -3826A/G polymorphism in the promoter of the uncoupling protein-1 (UCP1) gene and its relations to obesity in Chinese population. METHODS: Three hundred and eighty-four subjects (257 non-obese and 127 obese individuals) from a population of Chinese Han nationality in Chengdu area were studied using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLPs). Serum lipids were measured by enzymatic kits and apolipoproteins A I, A II, B100, C II, C III and E were measured by the RID kits. RESULTS: The frequencies of A and G alleles at -3826A/G site in obese and non-obese groups were 0.508 and 0.492, and 0.467 and 0.533, respectively. It showed no significant difference in allele frequencies between non-obese and obese groups (P > 0.05). In the obese group, subjects with genotype GG had higher serum apo B100 concentrations, and those with genotype AG had higher apo C II and apo C III levels, than those with genotype AA, respectively (P < 0.05). In non-obese male subgroup, subjects with genotype GG had lower serum HDL-C and apo A I levels than those with genotype AA, respectively (P < 0.05), whereas those with genotype AG had lower apo A II levels than those with genotype AA. In addition, in obese males with genotype GG had elevated apo B100 levels compared with those with genotype AA, whereas in obese females with genotype GG had decreased apo AI levels and genotype AG had increased apo C II and apo C III levels compared with those with genotype AG and AA, respectively (P < 0.05). CONCLUSION: -3826A/G polymorphism in the promoter of the uncoupling protein-1 gene was not associated with obesity in Chinese Han population of Chengdu area. It may be associated with serum HDL-C, apo A I and apo B100 levels in non-obese and/or obese subjects of certain genders.