Nomograms for predicting adverse obstetric outcome in IVF pregnancy: A preliminary study.

BACKGROUND: In a previous study, we showed that the obstetric complication rate after in vitro fertilization (IVF) pregnancy was 40%. The main objective of our study was to determine maternal prognosis factors that influence the IVF pregnancy outcome. METHODS: We conducted an observational retrospective monocentric study between January 2014 and January 2018. Pregnancy over 22 gestational weeks (GW) obtained after IVF in our infertility clinic was included. Maternal characteristics and pregnancy outcome were collected. RESULTS: Data from 498 IVF pregnancies were analyzed. The most significant maternal prognosis factors for obstetric complications were maternal age above 40 years (OR 3,0 [95% IC 1,30-7,09], P = 0,010), twin pregnancies (3.8 [95% IC 1.49-9.99], P = .005), daily maternal smoking above 10 cigarettes (7.1 [95% IC 1.22-41.74], P = .029), maternal obesity (2.2 [95% IC 1.19-4.07], P = .012), endometriosis stages III and IV (6.4 [95% IC 1.52-27.04], P = .011), and history of ovarian hyperstimulation syndrome (OHSS) in early pregnancy (5.7 [95% IC 1.29-24.74], P = .021). Risk increase was independent of pregnancy type (singleton or twin) and allowed the elaboration of 2 nomograms. CONCLUSIONS: Our study showed a link between some maternal factors and increase in obstetric complications after IVF. Screening of these factors during preconceptional visit is essential to identify at high-risk pregnancies and adapt their monitoring.

Somatic and axonal LIGHT signaling elicit degenerative and regenerative responses in motoneurons, respectively.

A receptor-ligand interaction can evoke a broad range of biological activities in different cell types depending on receptor identity and cell type-specific post-receptor signaling intermediates. Here, we show that the TNF family member LIGHT, known to act as a death-triggering factor in motoneurons through LT-ßR, can also promote axon outgrowth and branching in motoneurons through the same receptor. LIGHT-induced axonal elongation and branching require ERK and caspase-9 pathways. This distinct response involves a compartment-specific activation of LIGHT signals, with somatic activation-inducing death, while axonal stimulation promotes axon elongation and branching in motoneurons. Following peripheral nerve damage, LIGHT increases at the lesion site through expression by invading B lymphocytes, and genetic deletion of Light significantly delays functional recovery. We propose that a central and peripheral activation of the LIGHT pathway elicits different functional responses in motoneurons.

Calreticulin levels determine onset of early muscle denervation by fast motoneurons of ALS model mice.

Although the precise signaling mechanisms underlying the vulnerability of some sub-populations of motoneurons in ALS remain unclear, critical factors such as metallo-proteinase 9 expression, neuronal activity and endoplasmic reticulum stress have been shown to be involved. In the context of SOD1(G93A) ALS mouse model, we previously showed that a two-fold decrease in calreticulin (CRT) is occurring in the vulnerable fast motoneurons. Here, we asked to which extent the decrease in CRT levels was causative to muscle denervation and/or motoneuron degeneration. Toward this goal, a hemizygous deletion of the crt gene in SOD1(G93A) mice was generated since the complete ablation of crt is embryonic lethal. We observed that SOD1(G93A);crt(+/-) mice display increased and earlier muscle weakness and muscle denervation compared to SOD1(G93A) mice. While CRT reduction in motoneurons leads to a strong upregulation of two factors important in motoneuron dysfunction, ER stress and mTOR activation, it does not aggravate motoneuron death. Our results underline a prevalent role for CRT levels in the early phase of muscle denervation and support CRT regulation as a potential therapeutic approach.

Reduced calreticulin levels link endoplasmic reticulum stress and Fas-triggered cell death in motoneurons vulnerable to ALS.

Cellular responses to protein misfolding are thought to play key roles in triggering neurodegeneration. In the mutant superoxide dismutase (mSOD1) model of amyotrophic lateral sclerosis (ALS), subsets of motoneurons are selectively vulnerable to degeneration. Fast fatigable motoneurons selectively activate an endoplasmic reticulum (ER) stress response that drives their early degeneration while a subset of mSOD1 motoneurons show exacerbated sensitivity to activation of the motoneuron-specific Fas/NO pathway. However, the links between the two mechanisms and the molecular basis of their cellular specificity remained unclear. We show that Fas activation leads, specifically in mSOD1 motoneurons, to reductions in levels of calreticulin (CRT), a calcium-binding ER chaperone. Decreased expression of CRT is both necessary and sufficient to trigger SOD1(G93A) motoneuron death through the Fas/NO pathway. In SOD1(G93A) mice in vivo, reductions in CRT precede muscle denervation and are restricted to vulnerable motor pools. In vitro, both reduced CRT and Fas activation trigger an ER stress response that is restricted to, and required for death of, vulnerable SOD1(G93A) motoneurons. Our data reveal CRT as a critical link between a motoneuron-specific death pathway and the ER stress response and point to a role of CRT levels in modulating motoneuron vulnerability to ALS.

A rare motor neuron deleterious missense mutation in the DPYSL3 (CRMP4) gene is associated with ALS.

The dihydropyrimidinase-like 3 (DPYSL3) or Collapsin Response Mediator Protein 4a (CRMP4a) expression is modified in neurodegeneration and is involved in several ALS-associated pathways including axonal transport, glutamate excitotoxicity, and oxidative stress. The objective of the study was to analyze CRMP4 as a risk factor for ALS. We analyzed the DPYSL3/CRMP4 gene in French ALS patients (n = 468) and matched-controls (n = 394). We subsequently examined a variant in a Swedish population (184 SALS, 186 controls), and evaluated its functional effects on axonal growth and survival in motor neuron cell culture. The rs147541241:A>G missense mutation occurred in higher frequency among French ALS patients (odds ratio = 2.99) but the association was not confirmed in the Swedish population. In vitro expression of mutated DPYSL3 in motor neurons reduced axonal growth and accelerated cell death compared with wild type protein. Thus, the association between the rs147541241 variant and ALS was limited to the French population, highlighting the geographic particularities of genetic influences (risks, contributors). The identified variant appears to shorten motor neuron survival through a detrimental effect on axonal growth and CRMP4 could act as a key unifier in transduction pathways leading to neurodegeneration through effects on early axon development.

α-Secretase-derived fragment of cellular prion, N1, protects against monomeric and oligomeric amyloid ß (Aß)-associated cell death.

In physiological conditions, both ß-amyloid precursor protein (ßAPP) and cellular prion (PrP(c)) undergo similar disintegrin-mediated α-secretase cleavage yielding N-terminal secreted products referred to as soluble amyloid precursor protein-α (sAPPα) and N1, respectively. We recently demonstrated that N1 displays neuroprotective properties by reducing p53-dependent cell death both in vitro and in vivo. In this study, we examined the potential of N1 as a neuroprotector against amyloid ß (Aß)-mediated toxicity. We first show that both recombinant sAPPα and N1, but not its inactive parent fragment N2, reduce staurosporine-stimulated caspase-3 activation and TUNEL-positive cell death by lowering p53 promoter transactivation and activity in human cells. We demonstrate that N1 also lowers toxicity, cell death, and p53 pathway exacerbation triggered by Swedish mutated ßAPP overexpression in human cells. We designed a CHO cell line overexpressing the London mutated ßAPP (APP(LDN)) that yields Aß oligomers. N1 protected primary cultured neurons against toxicity and cell death triggered by oligomer-enriched APP(LDN)-derived conditioned medium. Finally, we establish that N1 also protects neurons against oligomers extracted from Alzheimer disease-affected brain tissues. Overall, our data indicate that a cellular prion catabolite could interfere with Aß-associated toxicity and that its production could be seen as a cellular protective mechanism aimed at compensating for an sAPPα deficit taking place at the early asymptomatic phase of Alzheimer disease.

Subfertile patients underestimate their risk factors of reprotoxic exposure.

BACKGROUND: Exposure of men and women to environmental reprotoxic agents is associated with impaired fertility and pregnancy rates after assisted reproductive treatment (ART). Nevertheless, such exposures are generally not systematically assessed in current practice before ART and subfertile men are generally less explored than women. Our objective was to study subfertile men and women's level of knowledge about reprotoxic agents, their perception of their own risk factors and the correlation between perceived and identified circumstances of exposure. RESULTS: In our public university hospital, 390 subfertile patients (185 men and 185 women) requiring assisted reproduction technique (ART) treatment, completed a self-report questionnaire before consultation, in order to assess patients' knowledge of reprotoxic exposures, sources of information about them and perception of their own circumstances of exposure. Then a standardized questionnaire was used by the physician during the consultation to estimate domestic, environmental and occupational risk factors of reprotoxic exposures (RFRE). We compared the patients' perception of exposure with the estimated RFRE. The reprotoxic agents knowledge score of patients was 61%. Their main sources of information were the media (40%), the internet (22%) and gynecologists (15%). The standardized questionnaire identified RFRE in 265/390 patients (68%); risk factor was statistically more frequent in men (77%) than in women (59%) (p < 0.05). In total, 141 of the 265 patients with identified RFRE (53%) were aware of their risk factor of reprotoxic exposure. CONCLUSION: We identified risk factors of reprotoxic exposures in the majority of subfertile patients, more frequently in men than in women, and half of patients were not aware of their exposures. Patients' main sources of information were extra medical. Efforts should be made to inform patients, especially men, about potential reprotoxic exposure and to enhance medical training about reprotoxic agents, as recommended by international guidelines. The detection and correction of environmental exposures in subfertile men could improve their fecundity, but also their general health, which has been shown to be poorer than health of fertile men.

RéSUMé: CONTEXTE: L'exposition des hommes et des femmes à des agents reprotoxiques environnementaux est. associée à une atération de leur fertilité et des taux de grossesse après assistance médicale à la procreation (AMP). Néanmoins, ces expositions ne sont généralement pas recherchées en pratique courante avant AMP et les hommes infertiles sont généralement moins explorés que les femmes. Notre objectif était d'analyser le niveau de connaissance des hommes et des femmes infertiles sur les expositions environnementales reprotoxiques, leur perception de leurs propres facteurs de risque et la correlation entre les expositions reprotoxiques perçues et celles identifiées. RESULTATS: Dans notre centre hospitalier universitaire, 390 patients infertiles (185 hommes et 185 femmes) nécessitant un traitement d'AMP ont complété un auto-questionnaire avant la consultation, afin d'évaluer leurs connaissances sur les expositions reprotoxiques, leurs sources d'information sur ce sujet, et leur perception de leurs propres expositions. Puis, lors de la consultation, le médecin utilisait un questionnaire standardisé pour estimer leurs facteurs de risque d'exposition reprotoxique (FRER) domestiques, environnementaux et professionnels. Nous avons comparé la perception par les patients de leurs propres expositions reprotoxiques avec le FRER estimé par le médecin. Le score de connaissance des agents reprotoxique des patients était de 61%. Leurs sources d'information principales étaient les medias (40%), internet (22%), et les gynécologues (15%). Le questionnaire standardisé identifiait un FRER chez 265/390 patients (68%); les FRER étaient significativement plus fréquents chez les hommes (77%) que chez le femmes (59%)(p < 0.05). Au total, 141 patients sur les 265 avec un FRER identifié étaient conscients de leur FRER. CONCLUSION: Nous avons identifié des facteurs de risque d'exposition reprotoxiques chez la majorité des patients infertiles, plus fréquemment chez les hommes que chez les femmes, et la moitié des patients n'étaient conscients de ces expositions. Les principals sources d'information des patients étaient extra-médicales. Des efforts sont nécessaires pour informer les patients, en particulier les hommes, sur les potentielles expositions reprotoxiques comme souligné par les recommandations internationales. La detection et la correction des expositions environnementales chez les hommes infertiles pourraient améliorer leur fécondité, mais aussi leur santé, qui a été démontrée comme moins bonne que celle des hommes fertiles.

p53-Dependent transcriptional control of cellular prion by presenilins.

The presenilin-dependent gamma-secretase processing of the beta-amyloid precursor protein (betaAPP) conditions the length of the amyloid beta peptides (Abeta) that accumulate in the senile plaques of Alzheimer's disease-affected brains. This, together with an additional presenilin-mediated epsilon-secretase cleavage, generates intracellular betaAPP-derived fragments named amyloid intracellular domains (AICDs) that regulate the transcription of several genes. We establish that presenilins control the transcription of cellular prion protein (PrP(c)) by a gamma-secretase inhibitor-sensitive and AICD-mediated process. We demonstrate that AICD-dependent control of PrP(c) involves the tumor suppressor p53. Thus, p53-deficiency abolishes the AICD-mediated control of PrP(c) transcription. Furthermore, we show that p53 directly binds to the PrP(c) promoter and increases its transactivation. Overall, our study unravels a transcriptional regulation of PrP(c) by the oncogene p53 that is directly driven by presenilin-dependent formation of AICD. Furthermore, it adds support to previous reports linking secretase activities involved in betaAPP metabolism to the physiology of PrP(c).

The alpha-secretase-derived N-terminal product of cellular prion, N1, displays neuroprotective function in vitro and in vivo.

Cellular prion protein (PrP(c)) undergoes a disintegrin-mediated physiological cleavage, generating a soluble amino-terminal fragment (N1), the function of which remained unknown. Recombinant N1 inhibits staurosporine-induced caspase-3 activation by modulating p53 transcription and activity, whereas the PrP(c)-derived pathological fragment (N2) remains biologically inert. Furthermore, N1 protects retinal ganglion cells from hypoxia-induced apoptosis, reduces the number of terminal deoxynucleotidyltransferase-mediated biotinylated UTP nick end labeling-positive and p53-immunoreactive neurons in a pressure-induced ischemia model of the rat retina and triggers a partial recovery of b-waves but not a-waves of rat electroretinograms. Our work is the first demonstration that the alpha-secretase-derived PrP(c) fragment N1, but not N2, displays in vivo and in vitro neuroprotective function by modulating p53 pathway. It further demonstrates that distinct N-terminal cleavage products of PrP(c) harbor different biological activities underlying the various phenotypes linking PrP(c) to cell survival.

Assessment of a Screening Questionnaire to Identify Exposure to Lead in Pregnant Women.

Lead readily crosses the placenta and displays adverse effects on birth outcomes and neurodevelopment. Systematic identification of the risk of exposure during pregnancy is essential but rarely performed, probably due to hospital staff's workload and their lack of awareness. We aimed to evaluate the relevance of a questionnaire to screen pregnant women for lead exposure. A cross-sectional, multicentre study was carried out on a population of 792 pregnant women from February 2018 to May 2020. A total of 596 women had a blood lead test: 68.5% had blood lead levels below 10 µg/L. The estimated prevalence above 25 µg/L was 4% (95% confidence interval (CI) [2.6-5.9]) and 1.3% had levels above 50 µg/L (95% CI [0.6-2.6]). Multivariate analysis showed that three risk factors significantly increased the probability of blood lead levels above 25 µg/L: the use of traditional cosmetics (adjusted odds ratio [aOR]: 3.90; 95% CI [1.65-9.21]; p = 0.002), degraded old housing (aOR: 2.67; 95% CI [1.19-6.038]; p = 0.018), and (marginally) eating bread more than twice a day (aOR: 2.40; 95% CI [0.96-6.11]; p = 0.060). Our study reveals that a three-question tool can be used to quickly screen for the risk of lead exposure in our population and to trigger lead blood tests and special vigilance during pregnancy follow-up.

Presenilin-dependent transcriptional control of the Abeta-degrading enzyme neprilysin by intracellular domains of betaAPP and APLP.

Amyloid beta-peptide (Abeta), which plays a central role in Alzheimer's disease, is generated by presenilin-dependent gamma-secretase cleavage of beta-amyloid precursor protein (betaAPP). We report that the presenilins (PS1 and PS2) also regulate Abeta degradation. Presenilin-deficient cells fail to degrade Abeta and have drastic reductions in the transcription, expression, and activity of neprilysin, a key Abeta-degrading enzyme. Neprilysin activity and expression are also lowered by gamma-secretase inhibitors and by PS1/PS2 deficiency in mouse brain. Neprilysin activity is restored by transient expression of PS1 or PS2 and by expression of the amyloid intracellular domain (AICD), which is cogenerated with Abeta, during gamma-secretase cleavage of betaAPP. Neprilysin gene promoters are transactivated by AICDs from APP-like proteins (APP, APLP1, and APLP2), but not by Abeta or by the gamma-secretase cleavage products of Notch, N- or E- cadherins. The presenilin-dependent regulation of neprilysin, mediated by AICDs, provides a physiological means to modulate Abeta levels with varying levels of gamma-secretase activity.

M1 and M3 muscarinic receptors control physiological processing of cellular prion by modulating ADAM17 phosphorylation and activity.

The cellular prion protein (PrP(c)) undergoes a physiological processing yielding the N-terminal fragment referred to as N1, the production of which can be constitutive or protein kinase C regulated. We show that activation of endogenous muscarinic receptors by carbachol and by the M1-selective agonist AF267B increases N1 recovery in an atropine-sensitive manner, in mouse embryonic primary neurons. To identify the muscarinic receptor subtype involved, we used human embryonic kidney HEK293 (HEK) cells stably overexpressing M1, M2, M3, or M4 receptor subtype. Carbachol and the selective M1 agonist AF267B dose dependently increased N1 release by HEK-M3 and HEK-M1 cells, respectively, whereas carbachol did not modify N1 production by HEK-M2 or HEK-M4 cells. We demonstrate that the increase of N1 was not attributable to modified trafficking to the membrane of either PrP(c) or the disintegrin metalloproteases ADAM10 or ADAM17. Furthermore, we establish that carbachol affects the overall phosphorylation of ADAM17 on its threonine and tyrosine but not serine residues, whereas levels of phosphorylated ADAM9 were not affected. Interestingly, carbachol also increases the hydrolysis of the fluorimetric substrate JMV2770, which mimicked the sequence encompassing the N1 site cleavage and was shown previously to behave as an ADAM protease substrate. Mutations of threonine 735 but not of tyrosine 702 of the ADAM17 cytoplasmic tail abolishes the carbachol-induced increase of N1, ADAM17 phosphorylation, and JMV2770-hydrolyzing activity in M1- and M3-expressing HEK293 cells. Thus, our data provide strong evidence that muscarinic receptor activation increases the physiological processing of PrP(c) by upregulating the phosphorylation state and activity of ADAM17 protease.

Regulation of betaAPP and PrPc cleavage by alpha-secretase: mechanistic and therapeutic perspectives.

Alzheimer's disease (AD) is by far the most common form of dementia in the elderly and concerns one out of three individuals over 85. Like other neurodegenerative disorders such as Parkinson, Hungtington or prion diseases, AD is characterized by the formation of amyloid plaques in the central nervous system. In the brain of AD patients, the main component of these abnormal deposits is an aggregated form of the so-called amyloid beta-peptide (Abeta), which is produced from a large trans-membrane type-1 protein, the beta-amyloid precursor protein (betaAPP), by the sequential action of the beta- and gamma-secretases. Beside these two amyloidogenic proteolytic attacks, betaAPP is targeted by a third enzyme termed alpha-secretase. Of utmost importance, this cleavage, which can be of constitutive or regulated origin, occurs right in the middle of the Abeta sequence, thus precluding its production. For this reason, and because the sAPPalpha secreted fragment derived from this cleavage displays beneficial effects, tremendous efforts have been made recently in order to both identify the proteases involved and the way they are regulated. More recently, it emerged that alpha-secretase was also responsible for the physiological processing of the cellular prion protein (PrP(c)) in the middle of its toxic 106-126 sequence. This review will focus on the recent advances in the alpha-secretase pathways regulation and will discuss the putative therapeutic approaches that could be envisioned concerning the treatment of two apparently distinct diseases that share common denominators according to their metabolism.

Environmental Health in Perinatal and Early Childhood: Awareness, Representation, Knowledge and Practice of Southern France Perinatal Health Professionals.

The exposure of adults of reproductive age as well as pregnant women and children to environmental contaminants is of particular concern, as it can impact fertility, in utero development, pregnancy outcomes and child health. Consequently, the World Health Organisation (WHO) and international societies advocate including Environmental Health (EH) in perinatal care, yet perinatal health professionals (HPs) hardly put these recommendations into practice. In 2017, a cross-sectional study was performed in a large panel of perinatal HPs in south-eastern France with the aim of painting a picture of their current attitudes, representation, knowledge, and training expectations. Quantitative and qualitative information was collected via auto-questionnaire. Questionnaires were completed by 962 participants, mainly midwives (41.1%), physicians (25.6%) and nursery nurses (11%). Indoor/outdoor air quality and endocrine disruptors were the best-mastered topics, whereas electromagnetic fields and diet gave rise to unsure responses. Overall, perinatal HPs were ill-trained and -informed about the reproductive risks linked to daily environmental exposure. HPs reported scarce knowledge, fear of patient reaction and lack of solutions as the main barriers to providing information regarding EH to the public. Our findings highlight the need to set up EH training programmes focused on scientific knowledge and to provide simple messages and tips to help perinatal HPs deliver advice to populations to mitigate exposure to environmental toxicants.

Presenilin-dependent gamma-secretase-mediated control of p53-associated cell death in Alzheimer's disease.

Presenilins (PSs) are part of the gamma-secretase complex that produces the amyloid beta-peptide (Abeta) from its precursor [beta-amyloid precursor protein (betaAPP)]. Mutations in PS that cause familial Alzheimer's disease (FAD) increase Abeta production and trigger p53-dependent cell death. We demonstrate that PS deficiency, catalytically inactive PS mutants, gamma-secretase inhibitors, and betaAPP or amyloid precursor protein-like protein 2 (APLP2) depletion all reduce the expression and activity of p53 and lower the transactivation of its promoter and mRNA expression. p53 expression also is diminished in the brains of PS- or betaAPP-deficient mice. The gamma- and epsilon-secretase-derived amyloid intracellular C-terminal domain (AICD) fragments (AICDC59 and AICDC50, respectively) of betaAPP trigger p53-dependent cell death and increase p53 activity and mRNA. Finally, PS1 mutations enhance p53 activity in human embryonic kidney 293 cells and p53 expression in FAD-affected brains. Thus our study shows that AICDs control p53 at a transcriptional level, in vitro and in vivo, and that FAD mutations increase p53 expression and activity in cells and human brains.

The gamma/epsilon-secretase-derived APP intracellular domain fragments regulate p53.

Amyloid beta-peptide (Abeta), which plays a central role in Alzheimer Disease, is generated by presenilin-dependent and presenilin-independent gamma-secretase cleavages of beta-amyloid precursor protein (betaAPP). We report that the presenilins (PS1 and PS2) also regulate p53-associated cell death. Thus, we established that PS deficiency, catalytically inactive PS mutants, gamma-secretase inhibitors and betaAPP or APLP2 depletion reduced the expression and activity of p53, and lowered the transactivation of its promoter and mRNA levels. p53 expression was also reduced in the brains or betaAPP-deficient mice or in brains where both PS had been invalidated by double conditional knock out. AICDC59 and AICDC50, the gamma- and epsilon-secretase-derived C-terminal fragments of betaAPP, respectively, trigger the activation of caspase-3, p53-dependent cell death, and increase p53 activity and mRNA. Finally, HEK293 cells expressing PS1 harboring familial AD (FAD) mutations or FAD-affected brains, all display enhanced p53 activity and p53 expression. Our studies demonstrate that AICDs control p53 at a transcriptional level, in vitro and in vivo and unravel a still unknown function for presenilins.

Optimised and rapid pre-clinical screening in the SOD1(G93A) transgenic mouse model of amyotrophic lateral sclerosis (ALS).

The human SOD1(G93A) transgenic mouse has been used extensively since its development in 1994 as a model for amyotrophic lateral sclerosis (ALS). In that time, a great many insights into the toxicity of mutant SOD1 have been gained using this and other mutant SOD transgenic mouse models. They all demonstrate a selective toxicity towards motor neurons and in some cases features of the pathology seen in the human disease. These models have two major drawbacks. Firstly the generation of robust preclinical data in these models has been highlighted as an area for concern. Secondly, the amount of time required for a single preclinical experiment in these models (3-4 months) is a hurdle to the development of new therapies. We have developed an inbred C57BL/6 mouse line from the original mixed background (SJLxC57BL/6) SOD1(G93A) transgenic line and show here that the disease course is remarkably consistent and much less prone to background noise, enabling reduced numbers of mice for testing of therapeutics. Secondly we have identified very early readouts showing a large decline in motor function compared to normal mice. This loss of motor function has allowed us to develop an early, sensitive and rapid screening protocol for the initial phases of denervation of muscle fibers, observed in this model. We describe multiple, quantitative readouts of motor function that can be used to interrogate this early mechanism. Such an approach will increase throughput for reduced costs, whilst reducing the severity of the experimental procedures involved.

Transcriptional repression of p53 by parkin and impairment by mutations associated with autosomal recessive juvenile Parkinson's disease.

Mutations of the ubiquitin ligase parkin account for most autosomal recessive forms of juvenile Parkinson's disease (AR-JP). Several studies have suggested that parkin possesses DNA-binding and transcriptional activity. We report here that parkin is a p53 transcriptional repressor. First, parkin prevented 6-hydroxydopamine-induced caspase-3 activation in a p53-dependent manner. Concomitantly, parkin reduced p53 expression and activity, an effect abrogated by familial parkin mutations known to either abolish or preserve its ligase activity. ChIP experiments indicate that overexpressed and endogenous parkin interact physically with the p53 promoter and that pathogenic mutations abolish DNA binding to and promoter transactivation of p53. Parkin lowered p53 mRNA levels and repressed p53 promoter transactivation through its Ring1 domain. Conversely, parkin depletion enhanced p53 expression and mRNA levels in fibroblasts and mouse brains, and increased cellular p53 activity and promoter transactivation in cells. Finally, familial parkin missense and deletion mutations enhanced p53 expression in human brains affected by AR-JP. This study reveals a ubiquitin ligase-independent function of parkin in the control of transcription and a functional link between parkin and p53 that is altered by AR-JP mutations.

LRP1 controls biosynthetic and endocytic trafficking of neuronal prion protein.

The trafficking of normal cellular prion protein (PrPC) is believed to control its conversion to the altered conformation (designated PrPSc) associated with prion disease. Although anchored to the membrane by means of glycosylphosphatidylinositol (GPI), PrPC on neurons is rapidly and constitutively endocytosed by means of coated pits, a property dependent upon basic amino acids at its N-terminus. Here, we show that low-density lipoprotein receptor-related protein 1 (LRP1), which binds to multiple ligands through basic motifs, associates with PrPC during its endocytosis and is functionally required for this process. Moreover, sustained inhibition of LRP1 levels by siRNA leads to the accumulation of PrPC in biosynthetic compartments, with a concomitant lowering of surface PrPC, suggesting that LRP1 expedites the trafficking of PrPC to the neuronal surface. PrPC and LRP1 can be co-immunoprecipitated from the endoplasmic reticulum in normal neurons. The N-terminal domain of PrPC binds to purified human LRP1 with nanomolar affinity, even in the presence of 1 muM of the LRP-specific chaperone, receptor-associated protein (RAP). Taken together, these data argue that LRP1 controls both the surface, and biosynthetic, trafficking of PrPC in neurons.