Biology subjects

Ribacke, U.

Publications and source records attributed to Ribacke, U..

4 recordsLinked to original sources

bioRxiv2026

Intratumoral expression of JAML on NK cells is controlled by tumor microenvironment and MHC class I interaction

Junctional adhesion molecule-like (JAML) is an adhesion molecule known to promote T cell activation and T cell-mediated tumor rejection. In the current study, we show that JAML expression is enriched on mouse intratumoral NK cells compared with splenic NK cells. JAML+ NK cells were associated with tissue residency and co-expressed the immune checkpoints PD-1 and LAG3. JAML expression could be induced on splenic NK cells by IL-2 and further enhanced by IL-21. JAML levels were inversely correlated with inhibitory signaling, as NK cells expressing self-recognizing Ly49 receptors had reduced JAML expression, suggesting regulation of JAML expression by MHC class I molecules. Interaction with the JAML ligand CXADR also reduced JAML surface expression, indicating that tumor-mediated membrane stripping may represent a mechanism of immunoediting. Although JAML RNA transcripts were detectable in human NK cells, JAML protein was found only intracellularly. Together, these findings identify the JAML-CXADR interaction as a potential regulatory pathway in NK cell-mediated killing of tumors.

immunology↗

bioRxiv2025

Uncovering the genetic diversity of the malaria parasite antigen MSP2 across Sub-Saharan Africa

Genetic diversity in Plasmodium falciparum poses a significant challenge to malaria control and elimination. This is particularly important for developing fully efficacious vaccines, which should include valuable blood stage antigens. Several antigen candidates are highly diverse and require further understanding. We surveyed the genetic diversity of the highly polymorphic merozoite surface protein 2 (MSP2) in 2761 P. falciparum isolates collected across Sub-Saharan Africa. Using PCR-based genotyping and long-read sequencing, we identified extensive diversity among msp2 size variants and sequences. Some size variants were more prevalent than others across different geographical regions, transmission intensities, and time points. These variants comprised multiple unique sequences, of which several were geographically and temporally widespread. Our study reveals greater msp2 sequence diversity than previously known, while also identifying interesting similarities in sequence and gene length across Sub-Saharan Africa. These findings support the further exploration of common msp2 variants in relation to parasite virulence and vaccine development.

microbiology↗

bioRxiv2023

Epigenetics and chromatin structure regulate var2csa expression and the placental binding phenotype in Plasmodium falciparum

Plasmodium falciparum is responsible for what appears to be a never-ending public health issue in the developing world. With repeated infections, a gradual semi-immunity to severe malaria can be acquired but this is disrupted when women become pregnant as the parasite cytoadheres in the placenta to prevent splenic clearance. This change in tissue tropism is due to specific transcription of the antigenically variable adhesin VAR2CSA. To better understand the molecular mechanisms activating var2csa and antigenic variation overall, we used a combination of phenotypic and systems biology assays. We first established phenotypically homogenous populations of VAR2CSA expressing and placenta binding parasites that were shown to exclusively transcribe var2csa while all other var genes remained silenced. We also confirmed that the transcriptional activation was strongly associated with distinct depletion of repressive H3K9me3 marks. Further, we used chromatin conformation capture as a high-resolution approach to determine interchromosomal interactions and established that transcriptional activation is linked to a small yet significant repositioning of var2csa relative to heterochromatic telomeric clusters. Lastly, we demonstrated that occupancy of 5-methylcytosine was present in all var genes but independent of transcriptional repression and switching. All together, these findings provide insights at high resolution into the potential role of 5-methylcytosine in P. falciparum and increase our understanding of the mechanisms regulating antigenic variation at the epigenetics and chromatin structure level.

cell biology↗

bioRxiv2023

Genomic adaptation underlies nutrient-driven reprogramming in the malaria-causing parasite

Parasites often depend on metabolic adaptation to the host environment. An adaptive feature of malaria-causing parasites is digestion of hemoglobin (HB) to acquire amino acids (AAs). Here we describe a link between nutrient availability and translation elongation-dependent regulation of gene expression as an adaptive strategy. We show that, unexpectedly, tRNA expression in P. falciparum does not match the decoding need as tRNAs decoding AAs that are rare in HB are lowly expressed. This discrepancy renders codons of HB-rare AAs inefficiently decoded and transcripts levels negatively correlated with the requirement of HB-rare AAs for protein synthesis, which are consistent with poor codon optimality causing co-translational mRNA decay. Intriguingly, proliferation-related genes have evolved to require a high level of HB-rare AAs in their encoded proteins, thereby allowing the parasite to control its proliferation by repressing protein synthesis of these genes during nutrient stress. We conclude that the parasite modulates translation elongation by maintaining a discordant tRNA profile as a mechanism to exploit variations in AA-composition among genes as an adaptation strategy.

microbiology↗