Phosphorylation at the disordered N-end makes HuR accumulate and dimerize in the cytoplasm.

Human antigen R (HuR) is an RNA binding protein mainly involved in maintaining the stability and controlling the translation of mRNAs, critical for immune response, cell survival, proliferation and apoptosis. Although HuR is a nuclear protein, its mRNA translational-related function occurs at the cytoplasm, where the oligomeric form of HuR is more abundant. However, the regulation of nucleo-cytoplasmic transport of HuR and its connection with protein oligomerization remain unclear. In this work, we describe the phosphorylation of Tyr5 as a new hallmark for HuR activation. Our biophysical, structural and computational assays using phosphorylated and phosphomimetic HuR proteins demonstrate that phosphorylation of Tyr5 at the disordered N-end stretch induces global changes on HuR dynamics and conformation, modifying the solvent accessible surface of the HuR nucleo-cytoplasmic shuttling (HNS) sequence and releasing regions implicated in HuR dimerization. These findings explain the preferential cytoplasmic accumulation of phosphorylated HuR in HeLa cells, aiding to comprehend the mechanisms underlying HuR nucleus-cytoplasm shuttling and its later dimerization, both of which are relevant in HuR-related pathogenesis.

GWAS of genetic factors affecting white blood cell morphological parameters in Sardinians uncovers influence of chromosome 11 innate immunity gene cluster on eosinophil morphology.

Few genome-wide association studies (GWAS) analyzing genetic regulation of morphological traits of white blood cells have been reported. We carried out a GWAS of 12 morphological traits in 869 individuals from the general population of Sardinia, Italy. These traits, included measures of cell volume, conductivity and light scatter in four white-cell populations (eosinophils, lymphocytes, monocytes, neutrophils). This analysis yielded seven statistically significant signals, four of which were novel (four novel, PRG2, P2RX3, two of CDK6). Five signals were replicated in the independent INTERVAL cohort of 11 822 individuals. The most interesting signal with large effect size on eosinophil scatter (P-value = 8.33 x 10-32, beta = -1.651, se = 0.1351) falls within the innate immunity cluster on chromosome 11, and is located in the PRG2 gene. Computational analyses revealed that a rare, Sardinian-specific PRG2:p.Ser148Pro mutation modifies PRG2 amino acid contacts and protein dynamics in a manner that could possibly explain the changes observed in eosinophil morphology. Our discoveries shed light on genetics of morphological traits. For the first time, we describe such large effect size on eosinophils morphology that is relatively frequent in Sardinian population.

Pharmacokinetics and Safety of Lurbinectedin Administrated with Itraconazole in Cancer Patients: A Drug-Drug Interaction Study.

This open-label, two-part, phase Ib drug-drug interaction study investigated whether the pharmacokinetic (PK) and safety profiles of lurbinectedin (LRB), a marine-derived drug, are affected by co-administration of itraconazole (ITZ), a strong CYP3A4 inhibitor, in adult patients with advanced solid tumors. In Part A, three patients were sequentially assigned to Sequence 1 (LRB 0.8 mg/m2, 1-h intravenous [IV] + ITZ 200 mg/day oral in Cycle 1 [C1] and LRB alone 3.2 mg/m2, 1 h, IV in Cycle 2 [C2]). In Part B, 11 patients were randomized (1:1) to receive either Sequence 1 (LRB at 0.9 mg/m2 + ITZ in C1 and LRB alone in C2) or Sequence 2 (LRB alone in C1 and LRB + ITZ in C2). Eleven patients were evaluable for PK analysis: three in Part A and eight in Part B (four per sequence). The systemic total exposure of LRB increased with ITZ co-administration: 15% for Cmax, area under the curve (AUC) 2.4-fold for AUC0-t and 2.7-fold for AUC0-∞. Co-administration with ITZ produced statistically significant modifications in the unbound plasma LRB PK parameters. The LRB safety profile was consistent with the toxicities described in previous studies. Co-administration with multiple doses of ITZ significantly altered LRB systemic exposure. Hence, to avoid LRB overexposure when co-administered with strong CYP3A4 inhibitors, an LRB dose reduction proportional to CL reduction should be applied.

Genomic and Immunologic Correlates in Prostate Cancer with High Expression of KLK2.

The identification of surfaceome proteins is a main goal in cancer research to design antibody-based therapeutic strategies. T cell engagers based on KLK2, a kallikrein specifically expressed in prostate cancer (PRAD), are currently in early clinical development. Using genomic information from different sources, we evaluated the immune microenvironment and genomic profile of prostate tumors with high expression of KLK2. KLK2 was specifically expressed in PRAD but it was not significant associated with Gleason score. Additionally, KLK2 expression did not associate with the presence of any immune cell population and T cell activating markers. A mild correlation between the high expression of KLK2 and the deletion of TMPRSS2 was identified. KLK2 expression associated with high levels of surface proteins linked with a detrimental response to immune checkpoint inhibitors (ICIs) including CHRNA2, FAM174B, OR51E2, TSPAN1, PTPRN2, and the non-surface protein TRPM4. However, no association of these genes with an outcome in PRAD was observed. Finally, the expression of these genes in PRAD did not associate with an outcome in PRAD and any immune populations. We describe the immunologic microenvironment on PRAD tumors with a high expression of KLK2, including a gene signature linked with an inert immune microenvironment, that predicts the response to ICIs in other tumor types. Strategies targeting KLK2 with T cell engagers or antibody-drug conjugates will define whether T cell mobilization or antigen release and stimulation of immune cell death are sufficient effects to induce clinical activity.

Home Blood Pressure Self-monitoring plus Self-titration of Antihypertensive Medication for Poorly Controlled Hypertension in Primary Care: the ADAMPA Randomized Clinical Trial.

BACKGROUND: Patient empowerment through pharmacological self-management is a common strategy in some chronic diseases such as diabetes, but it is rarely used for controlling blood pressure. OBJECTIVE: This study aimed to assess self-monitoring plus self-titration of antihypertensive medication versus usual care for reducing systolic blood pressure (SBP) at 12 months in poorly controlled hypertensive patients. DESIGN: The ADAMPA study was a pragmatic, controlled, randomized, non-masked clinical trial with two parallel arms in Valencia, Spain. PARTICIPANTS: Hypertensive patients older than 40 years, with SBP over 145 mmHg and/or diastolic blood pressure (DBP) over 90 mmHg, were recruited from July 2017 to June 2018. INTERVENTION: Participants were randomized 1:1 to usual care versus an individualized, pre-arranged plan based on self-monitoring plus self-titration. MAIN MEASURE: The primary outcome was the adjusted mean difference (AMD) in SBP between groups at 12 months. KEY RESULTS: Primary outcome data were available for 312 patients (intervention n=156, control n=156) of the 366 who were initially recruited. The AMD in SBP at 12 months (main analysis) was -2.9 mmHg (95% CI, -5.9 to 0.1, p=0.061), while the AMD in DBP was -1.9 mmHg (95% CI, -3.7 to 0.0, p=0.052). The results of the subgroup analysis were consistent with these for the main outcome measures. More patients in the intervention group achieved good blood pressure control (<140/90 mmHg) at 12 months than in the control group (55.8% vs 42.3%, difference 13.5%, 95% CI, 2.5 to 24.5%, p=0.017). At 12 months, no differences were observed in behavior, quality of life, use of health services, or adverse events. CONCLUSION: Self-monitoring plus self-titration of antihypertensive medication based on an individualized pre-arranged plan used in primary care may be a promising strategy for reducing blood pressure at 12 months compared to usual care, without increasing healthcare utilization or adverse events. TRIAL REGISTRATION: EudraCT, number 2016-003986-25 (registered 17 March 2017) and clinicaltrials.gov , NCT03242785.

Distal Endarterectomy Combined With Endovascular Proximal Treatment: The Hybrid DEEP Retrograde Technique for High-Complexity Infrainguinal Disease.

Purpose: We present a hybrid technique for the treatment of chronic limb-threatening ischemia (CLTI) due to complex, multilevel infrainguinal disease. It consists of an open distal endarterectomy combined with endovascular proximal treatment (the DEEP technique). Materials and Methods: This was a prospective cohort study. Thirty-three limbs (30 patients) were treated. Main inclusion criteria were absence of significant disease in femoral bifurcation associated with a complex infrainguinal pattern. This approach was specially considered in absence of suitable vein for bypass, obesity, hostile groin, and overall high surgical risk. Results: Mean age was 72.8 ± 10 years (ranging 50-93). Most cases presented with severe limb threatening onset (90.9% Rutherford >4 and 81.8% WIfi >3) due to high-complexity infrainguinal disease pattern (Global Limb Anatomic Staging System [GLASS] stage III) in 31/33 (93.9%), chronic total occlusions (CTOs) in 24/33 (72.7%), and severe calcification (Peripheral Arterial Calcium Scoring System [PACSS] grade 4) in 22/33 (66.6%). Mean lesion length was 228.2 mm ± 83 (ranging 40-340 mm). In all procedures, a covered-stent (25 cm length Viabahn) was implanted in a retrograde fashion as the endovascular component. Effective revascularization was achieved in all cases, showing significant clinical and hemodynamic improvement (median pre- and postprocedure ankle-brachial index [ABI]: 0.3 and 0.9, respectively). Results at 12 months follow-up were as follows: 93.9% limb salvage ratio, 75.7% primary patency, 84.6% assisted primary patency, and 90.9% secondary patency. Major adverse limb events (MALE) and cardiovascular events (MACE) occurred in 8/33 (24.2%) and 2/33 (6%), respectively. Mean length of postoperative stay was 7.5 ± 6.92 days (3-27). Conclusion: This less invasive hybrid technique has promising short-term results for limb salvage and it is worth to be included in vascular armamentarium for CLTI revascularization in selected patients.

Corneal tissue changes following short-term soft contact lens wear of different materials.

PURPOSE: To study the effect of different soft contact lens (CL) materials during short-term wear on corneal tissue. METHODS: Twenty-two healthy participants wore both silicone hydrogel (MyDay, CooperVision) and hydrogel soft CLs (Biomedics 1 day extra, CooperVision) for 8 h per lens. In each session, Scheimpflug images were captured before and immediately after CL removal. Images were analysed using the densitometry distribution analysis, a technique from which two parameters, α (corneal transparency) and ß (corneal homogeneity), were estimated. In addition, the central corneal thickness changes after CL wear and the influence of the CL material on corneal transparency were evaluated. RESULTS: The ß parameter (homogeneity) increased by 5% after wearing both CL materials (paired t-test, p < 0.001). However, the α parameter (transparency) only increased in half of the participants. No material was found to be more determinant in causing the corneal densitometry changes. Statistically significant but not clinically relevant changes in corneal thickness were observed. CONCLUSIONS: Biomarkers of corneal tissue integrity (α and ß) were affected by short-term soft contact lens wear. The observed changes in corneal transparency and homogeneity were not clinically relevant but support the importance of participant-material biocompatibility.

Emoji-SP, the Spanish emoji database: Visual complexity, familiarity, frequency of use, clarity, and emotional valence and arousal norms for 1031 emojis.

This article presents subjective norms for 1031 emojis in six dimensions: visual complexity, familiarity, frequency of use, clarity, emotional valence, and emotional arousal. This is the largest normative study conducted so far that relies on subjective ratings. Unlike the few existing normative studies, which mainly comprise face emojis, here we present a wide range of emoji categories. We also examine the correlations between the dimensions assessed. Our results show that, in terms of their affective properties, emojis are analogous to other stimuli, such as words, showing the expected U-shaped relationship between valence and arousal. The relationship between affective properties and other dimensions (e.g., between valence and familiarity) is also similar to the relationship observed in words, in the sense that positively valenced emojis are more familiar than negative ones. These findings suggest that emojis are suitable stimuli for studying affective processing. Emoji-SP will be highly valuable for researchers of various fields interested in emojis, including computer science, communication, linguistics, and psychology. The full set of norms is available at: https://osf.io/dtfjv/ .

Proposed mechanism for regulation of H2 O2 -induced programmed cell death in plants by binding of cytochrome c to 14-3-3 proteins.

Programmed cell death (PCD) is crucial for development and homeostasis of all multicellular organisms. In human cells, the double role of extra-mitochondrial cytochrome c in triggering apoptosis and inhibiting survival pathways is well reported. In plants, however, the specific role of cytochrome c upon release from the mitochondria remains in part veiled yet death stimuli do trigger cytochrome c translocation as well. Here, we identify an Arabidopsis thaliana 14-3-3ι isoform as a cytosolic cytochrome c target and inhibitor of caspase-like activity. This finding establishes the 14-3-3ι protein as a relevant factor at the onset of plant H2 O2 -induced PCD. The in vivo and in vitro studies herein reported reveal that the interaction between cytochrome c and 14-3-3ι exhibits noticeable similarities with the complex formed by their human orthologues. Further analysis of the heterologous complexes between human and plant cytochrome c with plant 14-3-3ι and human 14-3-3ε isoforms corroborated common features. These results suggest that cytochrome c blocks p14-3-3ι so as to inhibit caspase-like proteases, which in turn promote cell death upon H2 O2 treatment. Besides establishing common biochemical features between human and plant PCD, this work sheds light onto the signaling networks of plant cell death.

ARL15 modulates magnesium homeostasis through N-glycosylation of CNNMs.

Cyclin M (CNNM1-4) proteins maintain cellular and body magnesium (Mg2+) homeostasis. Using various biochemical approaches, we have identified members of the CNNM family as direct interacting partners of ADP-ribosylation factor-like GTPase 15 (ARL15), a small GTP-binding protein. ARL15 interacts with CNNMs at their carboxyl-terminal conserved cystathionine-ß-synthase (CBS) domains. In silico modeling of the interaction between CNNM2 and ARL15 supports that the small GTPase specifically binds the CBS1 and CNBH domains. Immunocytochemical experiments demonstrate that CNNM2 and ARL15 co-localize in the kidney, with both proteins showing subcellular localization in the endoplasmic reticulum, Golgi apparatus and the plasma membrane. Most importantly, we found that ARL15 is required for forming complex N-glycosylation of CNNMs. Overexpression of ARL15 promotes complex N-glycosylation of CNNM3. Mg2+ uptake experiments with a stable isotope demonstrate that there is a significant increase of 25Mg2+ uptake upon knockdown of ARL15 in multiple kidney cancer cell lines. Altogether, our results establish ARL15 as a novel negative regulator of Mg2+ transport by promoting the complex N-glycosylation of CNNMs.

Hybrid revascularization of chronic limb-threatening ischemia using popliteal below-knee and tibial trifurcation open endarterectomy distally plus inter-woven nitinol stenting proximally.

OBJECTIVES: Chronic limb-threatening ischemia (CLTI) is frequently due to multilevel, heavily calcified lesions, and it is often associated with desert foot. Effective revascularization currently presents an additional challenge due to the increasing age, comorbidities, and frailty related to these patients. Pure endovascular treatment often fails to achieve effective and durable revascularization and it is associated with still high amputation rates. We present a novel hybrid approach and discuss its usefulness for limb salvage in complex infrainguinal lesions. METHODS: Two no-option patients for both anatomical and medical-comorbidity reasons, were treated consecutively for CLTI. Both of them had prior failed percutaneous endovascular treatment, and bypass revascularization had been ruled out. We describe the technical details of an aggressive, but still less invasive hybrid approach, consisting of open distal popliteal artery (PA) and tibial trifurcation endarterectomy plus patch angioplasty, associated with proximal endovascular treatment with inter-woven nitinol stent from the superficial femoral artery (SFA) to the endarterectomized area. RESULTS: Technical success and salvage of the affected limb were achieved in both cases, presenting significant postoperative clinical and hemodynamic improvement and allowing early discharge hospital at home. There was no surgical wound infection or other complications. CONCLUSION: This hybrid approach through a single incision is safe and effective in the short term and can be used with excellent results for CLTI in high-risk and /or no-option patients.

Intestinal pneumatosis: a rare and misdiagnosed entity.

Intestinal pneumatosis is a rare entity, usually found incidentally, and in most cases asymptomatic. We present the case of an 84-year-old man who underwent colonoscopy for adenomatous polyps surveillance and presented typical endoscopic images of intestinal pneumatosis. Some of the most important aspects of the disease are highlighted and even if the endoscopic image is quite impressive, conservative management is the treatment of choice.

IUBMB focused meeting/FEBS workshop: Crosstalk between nucleus and mitochondria in human disease (CrossMitoNus).

The IUBMB Focused Meeting/FEBS Workshop titled 'Crosstalk between Nucleus and Mitochondria in Human Disease'(CrossMitoNus) will take place on September 7-10, 2021 in Seville (Spain), with the support of both the International Union of Biochemistry and Molecular Biology (IUBMB) and the Federation of European Biochemical Societies (FEBS). Mitochondria are key organelles that act as a hub for vital metabolic processes, for example, energy transduction by oxidative phosphorylation, intermediary metabolism, redox signaling, calcium and iron homeostasis, heme and steroid biosynthesis, metal homeostasis, programmed cell death, and innate immunity. Consequently, a wide assortment of diseases-including neurodegenerative disorders, diabetes, cancer, rare syndromes, and many others-relate to mitochondrial dysfunction. The high relevance of mitochondria in metabolism centers on the core of cell signaling pathways, including those involved in cell-fate decisions. Critical metabolites synthesized in mitochondria are, for instance, key modulators of the sirtuin, AMPK, mTOR, and Hypoxia-inducible Factor 1A pathways. Mitochondria are indeed the major source of reactive oxygen species, which in turn mediate several regulatory routes. Interestingly, multiple nuclear-encoded factors control essential processes in mitochondrial dynamics, namely fusion (for instance, OPA1), fission (DNM1L), transport (RHOT1), and mitophagy (PINK1). The release of mitochondrial factors like cytochrome c to the cytoplasm is indeed key for the rapid onset of the intrinsic apoptotic pathway. The CrossMitoNus meeting aims to join efforts from diverse disciplines to unveil the mitochondrial and nuclear factors that are emerging as essential elements in mitochondria-nucleus communication. Needless to say, the mechanisms regulating mitochondrial protein trafficking into and out of the nucleus and the role of these proteins in the nucleus remain to be elucidated.

Toxicity and antitumor activity of novel agents in elderly patients with cancer included in phase 1 studies.

Introduction The number of cancer cases among the elderly continue to increase as the worldwide population ages. This patient subset is underrepresented in clinical trials, partly because of unresolved uncertainties about age-associated tolerabilities and antitumor activities. We reviewed phase 1 trial data to study tolerance and efficacy of novel agents used for treatment of elderly patients with cancer. Methods Data from 773 consecutive evaluable patients in 85 phase 1 clinical trials (2008-2016) at START Madrid-CIOCC were analyzed according to age, with respect to objective response, survival, and toxicity. Results The mean age was 58.7 (range: 18-87) years; 260 (33.6%) patients were >65 y (elderly group). One hundred thirty-seven (17.8%) patients received immunotherapy drugs, 308 (39.8%) received targeted agents, and 328 (42.4%) received chemotherapy. No statistically significant differences in overall survival, objective response, or severe toxicity rates were found according to treatment type. Similar toxicities and clinical activities were found between the two age subgroups; 18.8% of the elderly and 20.7% of the younger patients experienced severe hematological toxicity (p=0.5), and 30.2% and 32.7%, respectively, experienced severe non-hematological toxicity (p=0.4). Regarding antitumor activity, 12.4% of the elderly and 15% of the younger patients achieved objective responses (p=0.41). There were no significant between-group differences in overall survival (9.7 versus 11.5 months, respectively, p=0.1) or progression-free survival (2.3 versus 2.2 months, respectively, p=0.7). Conclusions This retrospective study found that elderly and younger populations had comparable antitumor activities and toxicity profiles. These results support including elderly patients with cancer in early-phase trials.

A Predictive Score of Antitumour Activity of Novel Agents in Cancer Patients Treated in Early Phase Studies.

INTRODUCTION: Phase I trials aim to determine the maximum-tolerated dose of a particular drug while minimizing the number of patients exposed to either sub-therapeutic doses or severe toxicity. Thus, patient selection for phase I trials is a key component of any clinical trial design. Though several studies have been made to address this issue, patient selection still represents a major clinical challenge that needs further investigation. METHODS: Twenty-nine baseline clinical and analytical characteristics of 773 consecutive patients treated in phase I trials between 2008 and 2016 in START Madrid-CIOCC were analysed and correlated to objective response (OR), progression-free survival, median overall survival, toxicity, and treatment type. The ones associated to OR in the univariate analysis were included in the stepwise logistic regression multivariate and Cox analysis. The statistically significant ones were included in a predictive score (named here as the Madrid score) of antitumour activity. RESULTS: Body mass index (BMI) >25 (p = 0.027), two or less previous lines of treatment (p = 0.007), and normal levels of alkaline phosphatase (ALP) (p = 0.007) were found to positively correlate to radiological response. A Madrid score was generated using these three factors as predictive parameters: compared to a score of 2-3 (where 2 or 3 of these variables are altered), a score of 0-1 is associated with longer survival time (11.6 vs. 8.6 months; p = 0.005) and overall response (17 vs. 7.6%; p = 0.003). CONCLUSION: The predictive Madrid score, based on the BMI, number of prior lines of treatment, and ALP levels, might be helpful to accurately select patients who would benefit from oncology phase I clinical trials.

HuR biological function involves RRM3-mediated dimerization and RNA binding by all three RRMs.

HuR/ELAVL1 is an RNA-binding protein involved in differentiation and stress response that acts primarily by stabilizing messenger RNA (mRNA) targets. HuR comprises three RNA recognition motifs (RRMs) where the structure and RNA binding of RRM3 and of full-length HuR remain poorly understood. Here, we report crystal structures of RRM3 free and bound to cognate RNAs. Our structural, NMR and biochemical data show that RRM3 mediates canonical RNA interactions and reveal molecular details of a dimerization interface localized on the α-helical face of RRM3. NMR and SAXS analyses indicate that the three RRMs in full-length HuR are flexibly connected in the absence of RNA, while they adopt a more compact arrangement when bound to RNA. Based on these data and crystal structures of tandem RRM1,2-RNA and our RRM3-RNA complexes, we present a structural model of RNA recognition involving all three RRM domains of full-length HuR. Mutational analysis demonstrates that RRM3 dimerization and RNA binding is required for functional activity of full-length HuR in vitro and to regulate target mRNAs levels in human cells, thus providing a fine-tuning for HuR activity in vivo.

Oxidative stress is tightly regulated by cytochrome c phosphorylation and respirasome factors in mitochondria.

Respiratory cytochrome c has been found to be phosphorylated at tyrosine 97 in the postischemic brain upon neuroprotective insulin treatment, but how such posttranslational modification affects mitochondrial metabolism is unclear. Here, we report the structural features and functional behavior of a phosphomimetic cytochrome c mutant, which was generated by site-specific incorporation at position 97 of p-carboxymethyl-l-phenylalanine using the evolved tRNA synthetase method. We found that the point mutation does not alter the overall folding and heme environment of cytochrome c, but significantly affects the entire oxidative phosphorylation process. In fact, the electron donation rate of the mutant heme protein to cytochrome c oxidase, or complex IV, within respiratory supercomplexes was higher than that of the wild-type species, in agreement with the observed decrease in reactive oxygen species production. Direct contact of cytochrome c with the respiratory supercomplex factor HIGD1A (hypoxia-inducible domain family member 1A) is reported here, with the mutant heme protein exhibiting a lower affinity than the wild-type species. Interestingly, phosphomimetic cytochrome c also exhibited a lower caspase-3 activation activity. Altogether, these findings yield a better understanding of the molecular basis for mitochondrial metabolism in acute diseases, such as brain ischemia, and thus could allow the use of phosphomimetic cytochrome c as a neuroprotector with therapeutic applications.

Increased vulnerability of clinical research units during the COVID-19 crisis and their protection.

LAY SUMMARY: Currently, the complexity of clinical trial development in oncology is being further complicated by the coronavirus disease 2019 (COVID-19) pandemic, which is reducing the resources needed to comply with protocol-specific procedures while putting patients in units, who are already vulnerable, at increased general risk not only for COVID-19 infection but also with respect to their baseline disease. Individualizing the management of patients while ensuring their safety and adherence to the study protocol, establishing specific staff contingency plans, and maintaining sponsor and contract research organization (CRO) alignment are some of the key issues for maintaining the continuity of cancer patients' investigational treatment and minimizing their infection risk as well as the risk to staff members of the unit, sponsors, and CROs while maintaining the integrity of data quality and compliance with good clinical practice.

Structural basis of mitochondrial dysfunction in response to cytochrome c phosphorylation at tyrosine 48.

Regulation of mitochondrial activity allows cells to adapt to changing conditions and to control oxidative stress, and its dysfunction can lead to hypoxia-dependent pathologies such as ischemia and cancer. Although cytochrome c phosphorylation-in particular, at tyrosine 48-is a key modulator of mitochondrial signaling, its action and molecular basis remain unknown. Here we mimic phosphorylation of cytochrome c by replacing tyrosine 48 with p-carboxy-methyl-l-phenylalanine (pCMF). The NMR structure of the resulting mutant reveals significant conformational shifts and enhanced dynamics around pCMF that could explain changes observed in its functionality: The phosphomimetic mutation impairs cytochrome c diffusion between respiratory complexes, enhances hemeprotein peroxidase and reactive oxygen species scavenging activities, and hinders caspase-dependent apoptosis. Our findings provide a framework to further investigate the modulation of mitochondrial activity by phosphorylated cytochrome c and to develop novel therapeutic approaches based on its prosurvival effects.

Post-Translational Modifications of Cytochrome c in Cell Life and Disease.

Mitochondria are the powerhouses of the cell, whilst their malfunction is related to several human pathologies, including neurodegenerative diseases, cardiovascular diseases, and various types of cancer. In mitochondrial metabolism, cytochrome c is a small soluble heme protein that acts as an essential redox carrier in the respiratory electron transport chain. However, cytochrome c is likewise an essential protein in the cytoplasm acting as an activator of programmed cell death. Such a dual role of cytochrome c in cell life and death is indeed fine-regulated by a wide variety of protein post-translational modifications. In this work, we show how these modifications can alter cytochrome c structure and functionality, thus emerging as a control mechanism of cell metabolism but also as a key element in development and prevention of pathologies.