Peroxiredoxin 3 deficiency induces cardiac hypertrophy and dysfunction by impaired mitochondrial quality control

Mitochondrial quality control (MQC) consists of multiple processes: the prevention of mitochondrial oxidative damage, the elimination of damaged mitochondria via mitophagy and mitochondrial fusion and fission. Several studies proved that MQC impairment causes a plethora of pathological conditions including cardiovascular diseases. However, the precise molecular mechanism by which MQC reverses mitochondrial dysfunction, especially in the heart, is unclear. The mitochondria-specific peroxidase Peroxiredoxin 3 (Prdx3) plays a protective role against mitochondrial dysfunction by removing mitochondrial reactive oxygen species. Therefore, we investigated whether Prdx3-deficiency directly leads to heart failure via mitochondrial dysfunction. Fifty-two-week-old Prdx3-deficient mice exhibited cardiac hypertrophy and dysfunction with giant and damaged mitochondria. Mitophagy was markedly suppressed in the hearts of Prdx3-deficient mice compared to the findings in wild-type and Pink1-deficient mice despite the increased mitochondrial damage induced by Prdx3 deficiency. Under conditions inducing mitophagy, we identified that the damaged mitochondrial accumulation of PINK1 was completely inhibited by the ablation of Prdx3. We propose that Prdx3 interacts with the N-terminus of PINK1, thereby protecting PINK1 from proteolytic cleavage in damaged mitochondria undergoing mitophagy. Our results provide evidence of a direct association between MQC dysfunction and cardiac function. The dual function of Prdx3 in mitophagy regulation and mitochondrial oxidative stress elimination further clarifies the mechanism of MQC in vivo and thereby provides new insights into developing a therapeutic strategy for mitochondria-related cardiovascular diseases such as heart failure. © 20221

Differential Association between HERG and KCNE1 or KCNE2

The small proteins encoded by KCNE1 and KCNE2 have both been proposed as accessory subunits for the HERG channel. Here we report our investigation into the cell biology of the KCNE-HERG interaction. In a co-expression system, KCNE1 was more readily co-precipitated with co-expressed HERG than was KCNE2. When forward protein trafficking was prevented (either by Brefeldin A or engineering an ER-retention/retrieval signal onto KCNE cDNA) the intracellular abundance of KCNE2 and its association with HERG markedly increased relative to KCNE1. HERG co-localized more completely with KCNE1 than with KCNE2 in all the membrane-processing compartments of the cell (ER, Golgi and plasma membrane). By surface labeling and confocal immunofluorescence, KCNE2 appeared more abundant at the cell surface compared to KCNE1, which exhibited greater co-localization with the ER-marker calnexin. Examination of the extracellular culture media showed that a significant amount of KCNE2 was extracellular (both soluble and membrane-vesicle-associated). Taken together, these results suggest that during biogenesis of channels HERG is more likely to assemble with KCNE1 than KCNE2 due to distinctly different trafficking rates and retention in the cell rather than differences in relative affinity. The final channel subunit constitution, in vivo, is likely to be determined by a combination of relative cell-to-cell expression rates and differential protein processing and trafficking

Whole Exome Sequencing Reveals Severe Thrombophilia in Acute Unprovoked Idiopathic Fatal Pulmonary Embolism

Background: Acute unprovoked idiopathic fatal pulmonary embolism (IFPE) causes sudden death without an identifiable thrombogenic risk. We aimed to investigate the underlying genomic risks of IFPE through whole exome sequencing (WES). Methods: We reviewed 14 years of consecutive out-of-hospital fatal pulmonary embolism records (n = 1478) from the ethnically diverse population of New York City. We selected 68 qualifying IFPE cases for WES. We compared the WES data of IFPE cases to those of 9332 controls to determine if there is an excess of rare damaging variants in the genome using ethnicity-matched controls in collapsing analyses. Findings: We found nine of the 68 decedents (13·2%) who died of IFPE had at least one pathogenic or likely pathogenic variant in one of the three anti-coagulant genes: SERPINC1 (Antithrombin III), PROC, and PROS1. The odds ratio of developing IFPE as a variant carrier for SERPINC1 is 144·2 (95% CI, 26·3–779·4; P = 1·7 × 10−7), for PROC is 85·6 (95% CI, 13·0–448·9; P = 2.0 × 10−5), and for PROS1 is 56·4 (95% CI, 5·3–351·1; P = 0·001). The average age-at-death of anti-coagulant gene variant carriers is significantly younger than that of non-carriers (28·56 years versus 38·02 years; P = 0·01). Interpretation: This study showed the important role of severe thrombophilia due to natural anti-coagulant deficiency in IFPE. Evaluating severe thrombophilia in out-of-hospital fatal PE beyond IFPE is warranted

Molecular autopsy: using the discovery of a novel de novo pathogenic variant in the KCNH2 gene to inform healthcare of surviving family

Background: Molecular testing of the deceased (Molecular Autopsy) is an overlooked area in the United States healthcare system and is not covered by medical insurance, leading to ineffective care for surviving families of thousands of sudden unexpected natural deaths each year. We demonstrated the precision management of surviving family members through the discovery of a novel de novo pathogenic variant in a decedent. Methods: Forensic investigation and molecular autopsy were performed on an 18-year-old female who died suddenly and unexpectedly. Co-segregation family study of the first-degree relatives and functional characterization of the variant were conducted. Findings: We identified a novel nonsense variant, NP_000229.1:p.Gln1068Ter, in the long QT syndrome type II gene KCNH2 in the decedent. This finding correlated with her ante-mortem electrocardiograms. Patch clamp functional studies using transfected COS-7 cells show that hERG-ΔQ1068 has a mixed phenotype, with both gain- (negative voltage shift of steady-state activation curve, the positive shift of the steady-state inactivation curve, and accelerated activation) and loss-of function (reduced current density, reduced surface expression and accelerated deactivation) hallmarks. Loss of cumulative activation during rapid pacing demonstrates that the loss-of-function phenotype predominates. The wild-type channel did not rescue the hERG-ΔQ1068 defects, demonstrating haploinsufficiency of the heterozygous state. Targeted variant testing in the family showed that the variant in KCNH2 arose de novo, which eliminated the need for exhaustive genome testing and annual cardiac follow-up for the parents and four siblings. Interpretation: Molecular testing enables accurate determination of natural causes of death and precision care of the surviving family members in a time and cost-saving manner. We advocate for molecular autopsy being included under the healthcare coverage in US