Racial disparities in maternal mortality in the United States are urgently in need of greater attention and research. The prevalence of preeclampsia is higher among African American women than White women by 1.7-fold, and African American women are three times more likely to die from preeclampsia complications. Among African American patients, Apolipoprotein L1 protein (APOL1) gene variants are known to be linked to increased risk for non-diabetic chronic kidney disease (CKD). The Sub-Saharan African population is particularly affected by these risk variants, and they also have one of the highest rates of preeclampsia in the world. Variants in the APOL1 gene are common, with about 40-50% of African American individuals carrying one variant, suggesting that APOL1 may underlie other health conditions that disproportionately affect patients of recent African origin, including preeclampsia. Previous epidemiologic studies support an association between APOL1 variants in the fetus and preeclampsia risk. There are also indications that in the kidney podocytes, these variants increase the endoplasmic reticulum (ER) specific stress protein GRP78, also known to regulate trophoblast syncytialization in the placenta. Although previous studies are suggestive, the mechanisms by which APOL1 variants alter placental function to increase preeclampsia risk are not understood. We utilized immunofluorescence (IF) studies to probe APOL1 expression in first trimester placenta (6-7 weeks gestation), as well as reverse-transcription polymerase chain reaction (RT-PCR) and Western blot studies to probe basal expression of messenger ribonucleic acid (mRNA) and protein of both APOL1 and GRP78 in BeWo cells. Our results have laid the foundation for studies of the role APOL1 plays in the genesis of preeclampsia. / 2026-03-06T00:00:00Z

Yes / African trypanosomes, except Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense, which cause human African trypanosomiasis, are lysed by the human serum protein apolipoprotein L1 (ApoL1). These two subspecies can resist human ApoL1 because they express the serum resistance proteins T. b. gambiense glycoprotein (TgsGP) and serum resistance-associated protein (SRA), respectively. Whereas in T. b. rhodesiense, SRA is necessary and sufficient to inhibit ApoL1, in T. b. gambiense, TgsGP cannot protect against high ApoL1 uptake, so different additional mechanisms contribute to limit this uptake. Here we report a complex interplay between trypanosomes and an ApoL1 variant, revealing important insights into innate human immunity against these parasites. Using whole-genome sequencing, we characterized an atypical T. b. gambiense infection in a patient in Ghana. We show that the infecting trypanosome has diverged from the classical T. b. gambiense strains and lacks the TgsGP defense mechanism against human serum. By sequencing the ApoL1 gene of the patient and subsequent in vitro mutagenesis experiments, we demonstrate that a homozygous missense substitution (N264K) in the membrane-addressing domain of this ApoL1 variant knocks down the trypanolytic activity, allowing the trypanosome to avoid ApoL1-mediated immunity. IMPORTANCE. Most African trypanosomes are lysed by the ApoL1 protein in human serum. Only the subspecies Trypanosoma b. gambiense and T. b. rhodesiense can resist lysis by ApoL1 because they express specific serum resistance proteins. We here report a complex interplay between trypanosomes and an ApoL1 variant characterized by a homozygous missense substitution (N264K) in the domain that we hypothesize interacts with the endolysosomal membranes of trypanosomes. The N264K substitution knocks down the lytic activity of ApoL1 against T. b. gambiense strains lacking the TgsGP defense mechanism and against T. b. rhodesiense if N264K is accompanied by additional substitutions in the SRA-interacting domain. Our data suggest that populations with high frequencies of the homozygous N264K ApoL1 variant may be at increased risk of contracting human African trypanosomiasis. / This work, including the efforts of Stijn Deborggraeve, was funded by Research Foundation Flanders (1501413N). This work, including the efforts of Bart Cuypers, was funded by Research Foundation Flanders (11O1614N). This work, including the efforts of Jean-Claude Dujardin and Etienne Pays, was funded by Interuniversity Attraction Poles Program of Belgian Science Policy (P7/41). This work, including the efforts of Jean-Claude Dujardin, was funded by Flemish Ministry of Sciences (SOFI-B SINGLE). This work, including the efforts of Etienne Pays, was funded by EC | European Research Council (ERC) (APOLs 669007).

People of African ancestry (AA) are at greater risk of developing chronic kidney disease than those of non-AA. Much of this risk has been linked to specific genetic haplotypes on chromosome 22, near the genes APOL1, encoding apolipoprotein L1, and MYH9, encoding non-muscle myosin heavy chain IIA (NMHCIIA). The mechanisms by which the disease-associated chromosome 22 haplotypes promote kidney damage are unknown. Apolipoprotein L1 is a circulating protein with no known role in kidney function. However, the kidney disease-associated chromosome 22 haplotypes are protective against trypanosome infection, resulting in positive selective pressure for these haplotypes in western Africa, where trypanosome infection is endemic. In contrast, NMHCIIA may have an important role in glomerular function, and mutations in MYH9 are associated with glomerular disease, yet the disease-associated chromosome 22 haplotypes do not involve coding sequence variations in MYH9. With no clear disease-causing role for genes near the chromosome 22 risk locus, it is plausible that indirect mechanisms of gene regulation may be responsible for the increased disease risk. This study examines several potential pathways for kidney injury, including altered glomerular gene expression in carriers of chromosome 22 risk haplotypes, and the role of altered expression of MYH9 in podocyte cell biology and kidney disease. We found that carriers of chromosome 22 risk variants exhibited differential glomerular gene expression in pathways promoting kidney injury. We also found decreased glomerular NMHCIIA expression in human FSGS kidney biopsies, and altered cell structure and mechanical function when Myh9 is ablated in murine podocytes. Further, Myh9 podocyte deletion predisposed mice to glomerulopathy in response to injury by the DOCA-salt uninephrectomy model of hypertension. Taken together, these findings demonstrate direct and indirect effects of chromosome 22 risk variants on glomerular gene expression which promote kidney injury.

Apolipoprotein L1 (APOL1) is a human-specific serum protein bound to high-density lipoprotein (HDL) particles. This protein allows human resistance to infection by African trypanosomes except for two subspecies, Trypanosoma brucei rhodesiense and T. b. gambiense, the causative agents of sleeping sickness or African trypanosomiasis. This disease infects 20 000 people in sub-Saharan Africa and without treatment, infection is almost always fatal. T. b. rhodesiense resists APOL1 through direct protein neutralization by the Serum Resistance-Associated (SRA) protein. T. b. gambiense does not express SRA, and its mechanism of resistance to APOL1 is orchestrated upon a recently characterized multifactorial defense mechanism.<p><p>The mechanism by which the human serum sensitive parasites are killed following APOL1 uptake is described as the result of the lysosomal swelling induced by the generation of ionic pores within the lysosomal membrane.<p>We show here that preventing the osmotic lysosomal swelling in a hyperosmotic culture condition does not prevent the cell death. In addition, APOL1 appears to trigger some programmed cell death events in the cell such as a fast mitochondrial depolarization followed by a DNA laddering and fragmentation. Furthermore, we show an implication of the endonuclease G (TbEndoG), known to be a key actor in the regulation of cell death process and a kinesin (TbKIFC1), which might be the transporter of APOL1 for the endosomes to the mitochondrion.<p> <p>In addition, by producing different recombinant human APOL proteins in E. coli and test their activity on T. brucei, we were able to show that APOL3, an other member of the APOL family, also possesses a trypanolytic activity like APOL1 beneath the fact it is not a secreted protein. APOL3 does not only kill T. b. brucei but is also able to lyse APOL1-resistant subspecies such as rhodesiense and gambiense, in vitro and confirmed in vivo when the recombinant APOL3 were injected in infected mice. A beginning of an action mechanism is described herein showing a pH-independent activity for this protein oppositely to APOL1, conferring its specificity.<p>It is thus conceivable to use this recombinant protein as a first step of a potent curative agent against gambiense or rhodesiense since the few currently available drugs for treatment of African trypanosomiasis, that are outdated, show problems with toxicity and resistance. <p><p>/ <p><p>L’ Apolipoprotéine L1 (APOL1) est une protéine sérique humaine associée aux lipoprotéines de haute densité (HDL). Cette protéine confère la résistance à l'infection des trypanosomes africains à l'exception des deux sous-espèces, Trypanosoma brucei rhodesiense et T. b. gambiense, les agents responsables de la maladie du sommeil ou trypanosomiase africaine. Cette maladie infecte 20 000 personnes en Afrique sub-saharienne et en l'absence de traitement, l'infection est presque toujours mortelle. T. b. rhodesiense résiste à l’APOL1 grâce à une neutralisation directe d’APOL1 par une protéine appelé SRA (Serum Resistant-Associated). T. b. gambiense n'exprime pas SRA, et sa résistance à l’APOL1 est orchestrée par un mécanisme de défense multifactorielle récemment caractérisé 1.<p>Le mécanisme par lequel les parasites sensibles au sérum humain sont tués suivant l’entrée de l’APOL1 est décrit comme le résultat d’un gonflement du lysosome induit par la génération de pores ioniques à l'intérieur de la membrane lysosomiale2. Nous montrons ici que le gonflement osmotique du lysosome peut être empêché en condition de culture hyper osmotique, sans néanmoins empêcher la mort de la cellule. En outre, l’APOL1 semble déclencher des événements de mort cellulaire programmée dans la cellule, tels qu’une dépolarisation mitochondriale rapide suivie d'une fragmentation de l’ADN. De plus, nous montrons une implication de l'endonucléase G (TbEndoG), connu pour être un acteur clé dans la régulation du processus de mort cellulaire et d’une kinésine (TbKIFC1) qui pourrait avoir le rôle de transporter l’APOL1 des endosomes vers la mitochondrie.<p>Nous avons également pu montrer que l’APOL3, un autre membre de la famille des APOLs humaines, possède tout comme l’APOL1, une activité trypanolytique bien que cette protéine ne soit pas sécrétée en condition physiologique. De manière intéressante, l’APOL3 ne tue pas seulement T. b. brucei, mais est également capable de tuer les sous-espèces résistantes à l’APOL1 tels que rhodesiense et gambiense, in vitro et in vivo lorsque de l’APOL3 recombinante est injectée dans des souris infectées. La spécificité d’action de l’APOL3 pourrait être liée à une indépendance au pH, au contraire de l’APOL1. Il pourrait être envisagé d'utiliser cette protéine recombinante comme agent curatif contre gambiense ou rhodesiense du fait que les médicaments actuellement disponibles pour le traitement de la trypanosomiase africaine montrent des problèmes de toxicité et de résistance.<p><p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished