bioRxiv Science⌕ Search

Biology subjects

Merilahti, J.

Publications and source records attributed to Merilahti, J..

5 recordsLinked to original sources

YAP/TEAD drives treatment-induced adaptive immunosuppression in EGFR-mutant lung cancer

Residual disease remains a major obstacle for achieving durable responses in patients treated with oncogene-targeted therapy. Drug-tolerant persister (DTP) cells emerging under treatment and persisting in residual tumors are considered to be the root of acquired resistance, yet their contribution to immune evasion in on-treatment tumors is poorly defined. Here, we show in the context of EGFR-mutant lung cancer that DTP cells actively contribute to the formation of an immunosuppressive tumor microenvironment during EGFR tyrosine kinase inhibitor (TKI) therapy. In syngeneic mouse models and in patients, EGFR TKI therapy leads to an accumulation of immunosuppressive macrophages, which is strictly treatment-dependent and fully reversible upon treatment cessation or progressive disease, respectively. Quiescent DTP cells directly drive the recruitment and immunosuppressive reprogramming of monocytes and macrophages through a YAP-driven secretome, and the DTP-reprogrammed monocytes suppress T cell proliferation and effector functions in vitro. Co-targeting YAP with a TEAD inhibitor ORM-47286 rewires the DTP secretome and inhibits macrophage reprogramming in vitro, and prevents immunosuppressive macrophage accumulation and improves the efficacy of EGFR TKI therapy in immunocompetent mouse models. Our findings highlight the previously unappreciated role of DTP cells in modulating the tumor microenvironment in on-treatment tumors, and position the treatment-induced YAP/TEAD activity in DTP cells as an important driver of adaptive immunosuppression during EGFR-targeted therapy.

cancer biology↗

Coordinated action of CRK2 and QSK1 regulate osmotic stress response in Arabidopsis

Precise control of intercellular communication is essential for normal growth and stress responses in all multicellular organisms. In Arabidopsis, two membrane-localized receptor like kinases (RLKs), the Cysteine-rich RLK CRK2 and the Leucine-rich repeat (LRR) RLK QSK1 relocalize from the general plasma membrane (PM) to plasmodesmata (PD) in response to osmotic stress. Both these RLKs regulate callose deposition thereby modulating PD permeability. However, unchecked callose deposition can block the PD and disrupt proper intercellular communication. Here, we show that under normal growth conditions, CRK2 phosphorylates and sequesters QSK1 at the general PM, preventing unnecessary callose deposition at PD. We show that osmotic stress-induced enrichment of QSK1 at PD requires functional CRK2 and establish that phosphorylation of QSK1 in its C-terminal region is inhibitory in this process. We propose that osmotic stress triggers dephosphorylation and release of QSK1 from the CRK2-QSK1 complex, enabling its relocalization from general PM to PD, where it promotes stress-induced callose deposition. Subsequently, CRK2 relocalizes to PD where it negatively influences callose deposition. Our work reveals a tightly coordinated distribution of QSK1 and CRK2 at PM, establishing a dynamic gating mechanism that balances growth and stress responsiveness.

plant biology↗

CYSTEINE-RICH RLK2 regulates development via callose synthase-dependent symplastic transport in Arabidopsis

CYSTEINE-RICH RECEPTOR-LIKE PROTEIN KINASEs (CRKs) play an important role in plant development and stress responses. One of the best described members of the Arabidopsis CRK family is CRK2, which was proposed as a crucial regulator of intercellular transport facilitated by plasmodesmata (PD). As intercellular channels allowing symplastic communication, PD-mediated transport is predominantly regulated by callose synthase (CALS)-mediated callose deposition. This process can impact not just the distribution of molecules between adjacent cells, but also the symplastic loading of vascular tissue, thereby influencing plant stress responses and developmental processes. Here we described the overlapping expression pattern of genes encoding phylogenetically closely related CALS1 and CALS3. Both CALSs were phosphorylated in vitro by CRK2, and the genetic interaction between genes encoding CRK2 and CALS1 or CALS3 revealed their impact on callose deposition, rosette growth, primary root length, and development, represented as a decreased number of true leaves. Importantly, we observed significant accumulation of starch in crk2 mutant plants, especially in developmentally older leaves, which was reverted by the independent introduction of cals1.5 and cals3.1 into the crk2 mutant background. The observed starch accumulation was accompanied by photosynthesis inhibition. We propose that the growth and developmental alterations of crk2 are caused by decreased phloem loading, which resulted in starch accumulation in source organs, and subsequent sink tissue starvation. Our results propose CRK2 as negative regulator of CALS1 and CALS3 regulating source to sink transport, which impacts plant growth and development.

plant biology↗

LSD1 serine 166 is a phosphorylation switch for chromatinlandscaping, gene activation, and tissue remodeling

LSD1 is a histone 3 (H3) demethylase that can either repress or activate gene expression. We discover here that the so far enigmatic balance between these two activities in non-hormonal cancer cells is regulated by phosphorylation of serine 166 (S166) on LSD1. SET-mediated Protein Phosphatase 2A (PP2A) inhibition in KRAS mutant cells promotes S166 phosphorylation. Endogenous LSD1 S166 alanine mutant (S166A) cells display H3 lysine 9 demethylation and acetylation, euchromatin, and gene activation. Mechanistically this is explained by the impaired interaction of S166A mutant LSD1 with repressor proteins SNAI2 and MYBP1. Functionally LSD1 S166A mutant cells display augmented beta1 integrin activity and stress fiber formation, and the mutant xenograft tumors have altered tumor microenvironment associated with increased macrophage recruitment. Collectively, PP2A-regulated S166 of LSD1 is a phosphorylation switch for epigenetic gene activation in non-hormonal cancer cells. Conceptually we demonstrate how dephosphorylation of one amino acid on a non-histone protein shapes chromatin landscape in cancer cells, and modify tumor stroma, and immune cell content. Highlights* Mechanism for gene activation by LSD1 in non-hormonal cancers * Single phosphorylation switch in a non-histone protein controls epigenetic landscape * Epigenetic protein phosphorylation in cancer cells shapes tumour immune microenvironment * Novel function for Protein Phosphatase 2A (PP2A) in epigenome regulation via LSD1 Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=185 SRC="FIGDIR/small/653937v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@19548b3org.highwire.dtl.DTLVardef@1d7fd4dorg.highwire.dtl.DTLVardef@13707b3org.highwire.dtl.DTLVardef@1da7b71_HPS_FORMAT_FIGEXP M_FIG C_FIG

genomics↗

Phosphoproteomic analysis reveals the diversity of signaling behind ErbB inhibitor-induced phenotypes

The impact of kinase inhibitors on the phosphoproteome has been rarely investigated at a whole organism level. Here we performed a phosphoproteomic analysis in embryonic zebrafish to identify the signaling pathways perturbed by ErbB receptor tyrosine kinase inhibitors at the organism level. The phosphorylation of proteins associated with the PI3K/Akt, p38 MAPK, Notch, Hippo/Yap and {beta}-catenin signaling pathways were differentially regulated by the ErbB inhibitors. Gene set enrichment analyses indicated differential neurological and myocardial phenotypes of different ErbB inhibitors. To assess the neurological and myocardial effects, motility and ventricle growth assays were performed on zebrafish embryos treated with the ErbB and downstream signaling pathway inhibitors. The treatment with the inhibitors targeting the PI3K/Akt, p38 MAPK, and Notch signaling pathways along with the ErbB inhibitors AG1478 and Lapatinib perturbed the overall movement and ventricle wall growth of zebrafish embryos. Taken together, these results indicate that inhibitors with the same primary targets can affect different signaling pathways while eliciting similar physiological phenotypes.

cell biology↗