MAPK Module Research Articles

Modulation of Terpenoid Indole Alkaloid Biosynthesis in Catharanthus roseus by Sphingomonas Sp Y503 via the CrMAPKKK1-CrMAPKK1/CrMAPKK2-CrMPK3 Signaling Cascade.

Catharanthus roseus is a highly relevant model for investigating plant defense mechanisms and the biosynthesis of therapeutically valuable compounds, including terpenoid indole alkaloids (TIAs). It has been demonstrated that beneficial microbial interactions can regulate TIA biosynthesis in C. roseus, highlighting the need to fully comprehend the molecular mechanisms involved to efficiently implement eco-friendly strategies. This study explores the effects of a novel microbial strain, Y503, identified as Sphingomonas sp., on TIA production and the underlying mechanisms in C. roseus. Through bioinformatics analysis, we have identified 17 MAPKKKs, 7 MAPKKs, and 13 MAPKs within the C. roseus genome. Further investigation has verified the presence of the MAPK module (CrMAPKKK1-CrMAPKK1/CrMAPKK2-CrMPK3) mediating Y503 in regulating TIA biosynthesis in C. roseus. This study provides foundational information for strengthening the plant defense system in C. roseus through advantageous microbial interactions, which could contribute to the sustainable cultivation of medicinal plants such as C. roseus.

The MKK3 module integrates nitrate and light signals to modulate secondary dormancy in Arabidopsis thaliana

Seed dormancy corresponds to a reversible blockage of germination. Primary dormancy is established during seed maturation, while secondary dormancy is set up on the dispersed seed, following an exposure to unfavorable factors. Both dormancies are relieved in response to environmental factors, such as light, nitrate, and coldness. Quantitive Trait Locus (QTL) analyses for preharvest sprouting identified MKK3 kinase in cereals as a player in dormancy control. Here, we showed that MKK3 also plays a role in secondary dormancy in Arabidopsis within a signaling module composed of MAP3K13/14/19/20, MKK3, and clade-C MAPKs. Seeds impaired in this module acquired heat-induced secondary dormancy more rapidly than wild-type (WT) seeds, and this dormancy is less sensitive to nitrate, a signal able to release dormancy. We also demonstrated that MPK7 was strongly activated in the seed during dormancy release, especially in response to light and nitrate. This activation was greatly reduced in map3k13/14/19/20 and mkk3 mutants. Finally, we showed that the module was not regulated and apparently did not regulate the genes controlling abscisic acid/gibberellin acid hormone balance, one of the crucial mechanisms of seed dormancy control. Overall, our work identified a MAPK module controlling seed germination and enlarged the panel of functions of the MKK3-related modules in plants.

Leishmania surface molecule lipophosphoglycan-TLR2 interaction moderates TPL2-mediated TLR2 signalling for parasite survival.

Leishmania donovani, a protozoan parasite, resides and replicates in macrophages and inflicts the potentially fatal disease visceral leishmaniasis (VL). The parasite-expressed surface lipophosphoglycan (LPG) was implicated in binding TLR2 on NK cells, but the modus operandi of its disease-promoting influence remained unknown. As TPL2, a member of the MAPK module in mammalian macrophages, was implicated in the anti-inflammatory immune response and promoting pathogen survival, we investigated the possibility of TPL2-directed LPG-TLR2 signalling in Leishmania infection. We observed that TLR2 or TPL2 blockade differentially influenced the TLR2 ligand proteoglycan (PGN)-induced p38MAPK and ERK-1/2 activation. TLR2 blockade abrogated the PGN-induced TPL2 activation. L. donovani infection impaired the Akt activation whereas, upon TPL2 inhibition, the infection fails to control Akt phosphorylation. In L. donovani-infected macrophages, TLR2 blocking negatively affected p38, Akt and TPL2 phosphorylation while ERK1/2 phosphorylation increased relative to the infection alone. TPL2 blockade reduced TGF-β, but increased TNF-α expression and diminished amastigote count in macrophages. While exploring stimulation patterns of TLR2 ligands, LPG, unlike PGN, selectively increased TLR2 expression in macrophages. LPG blockade increased p38MAPK and AKT, but slightly affected ERK-1/2 and significantly reduced TPL2 phosphorylation from L. donovani-infected macrophages. Molecular docking and molecular dynamics analysis drew a parallel between LPG's glycan chain lengths with the frequency of interaction with TLR2 which might impact TLR2 signalling. Therefore, the parasite regulates the TLR2 signalling via TPL2 when elicited by LPG-TLR2 interaction for pathogenesis.

Temporal phosphoproteomic analysis of VEGF-A signaling in HUVECs: an insight into early signaling events associated with angiogenesis.

Vascular endothelial growth factor-A (VEGF-A) is one of the primary factors promoting angiogenesis in endothelial cells. Although defects in VEGF-A signaling are linked to diverse pathophysiological conditions, the early phosphorylation-dependent signaling events pertinent to VEGF-A signaling remain poorly defined. Hence, a temporal quantitative phosphoproteomic analysis was performed in human umbilical vein endothelial cells (HUVECs) treated with VEGF-A-165 for 1, 5 and 10min. This led to the identification and quantification of 1971 unique phosphopeptides corresponding to 961 phosphoproteins and 2771 phosphorylation sites in total. Specifically, 69, 153, and 133 phosphopeptides corresponding to 62, 125, and 110 phosphoproteins respectively, were temporally phosphorylated at 1, 5, and 10min upon addition of VEGF-A. These phosphopeptides included 14 kinases, among others. This study also captured the phosphosignaling events directed through RAC, FAK, PI3K-AKT-MTOR, ERK, and P38 MAPK modules with reference to our previously assembled VEGF-A/VEGFR2 signaling pathway map in HUVECs. Apart from a significant enrichment of biological processes such as cytoskeleton organization and actin filament binding, our results also suggest a role of AAK1-AP2M1 in the regulation of VEGFR endocytosis. Taken together, the temporal quantitative phosphoproteomics analysis of VEGF signaling in HUVECs revealed early signaling events and we believe that this analysis will serve as a starting point for the analysis of differential signaling across VEGF members toward the full elucidation of their role in the angiogenesis processes. Workflow for the identification of early phosphorylation events induced by VEGF-A-165 in HUVEC cells.

Mitogen-activated protein kinase 14-mediated phosphorylation of MaMYB4 negatively regulates banana fruit ripening.

Mitogen-activated protein kinase (MAPK/MPK) cascades play crucial parts in plant growth, development processes, immune ability, and stress responses; however, the regulatory mechanism by which MAPK affects fruit ripening remains largely unexplored. Here, we reported that MaMPK14 cooperated with MaMYB4 to mediate postharvest banana fruit ripening. Transient overexpression of individual MaMPK14 and MaMYB4 in banana fruit delayed fruit ripening, confirming the negative roles in the ripening. The ripening negative regulator MaMYB4 could repress the transcription of genes associated with ethylene biosynthesis and fruit softening, such as MaACS1, MaXTH5, MaPG3, and MaEXPA15. Furthermore, MaMPK14 phosphorylated MaMYB4 at Ser160 via a direct interaction. Mutation at Ser160 of MaMYB4 reduced its interaction with MaMPK14 but did not affect its subcellular localization. Importantly, phosphorylation of MaMYB4 by MaMPK14 enhanced the MaMYB4-mediated transcriptional inhibition, binding strength, protein stability, and the repression of fruit ripening. Taken together, our results delineated the regulation pathway of MAPK module during banana fruit ripening, which involved the phosphorylation modification of MaMYB4 mediated by MaMPK14.

The yeast two-component SLN1 branch of the HOG pathway and the scaffolding activity of Pbs2 modulate the response to endoplasmic reticulum stress induced by tunicamycin.

In addition to the UPR pathway, yeast cells require components of the HOG pathway to respond to ER stress. In this work, we found that unphosphorylated Sln1 and Ssk1 are required to mount an appropriate response to Tn. We also found that the MAPKKKs Ssk2 participates in the Tn response, but its osmo-redundant protein Ssk22 does not. We also found that the Pbs2 docking sites for Ssk2 (RDS-I and KD) are partially dispensable when mutated separately; however, the prevention of Ssk2 binding to Pbs2, by the simultaneous mutation of RDS-I and KD, caused strong sensitivity to Tn. In agreement with the lack of Hog1 phosphorylation during Tn treatment, a moderate resistance to Tn is obtained when a Pbs2 version lacking its kinase activity is expressed; however, the presence of mutual Pbs2-Hog1 docking sites is essential for the Tn response. Finally, we detected that Tn induced a transcriptional activation of some components of the SLN1 branch. These results indicate that the Tn response requires a complex formed by the MAPK module and components of the SLN1 branch but not their canonical osmoregulatory activities.

Analysis of human Tribbles 2 (TRIB2) pseudokinase.

Human Tribbles 2 (TRIB2) is a cancer-associated pseudokinase with a broad human protein interactome, including the well-studied AKT, C/EBPα and MAPK modules. Several lines of evidence indicate that human TRIB2 promotes cell survival and drug-resistance in solid tumors and blood cancers and is therefore of interest as a potential therapeutic target, although its physiological functions remain relatively poorly understood. The unique TRIB2 pseudokinase domain lacks the canonical 'DFG' motif, and subsequently possesses very low affinity for ATP in both the presence and absence of metal ions. However, TRIB2 also contains a unique cysteine-rich αC-helix, which interacts with a conserved peptide motif in its own carboxyl-terminal tail. This regulatory flanking region drives regulated interactions with distinct E3 ubiquitin ligases that serve to control the stability and turnover of TRIB2 client proteins. TRIB2 is also a low-affinity target of several known small-molecule protein kinase inhibitors, which were originally identified using purified recombinant TRIB2 proteins and a thermal shift assay. In this chapter, we discuss laboratory-based procedures for purification, stabilization and analysis of human TRIB2, including screening procedures that can be used for the identification of both reversible and covalent small molecule ligands.

Voyage of MAPK Modules in Plant Immunity

Evrimsel olarak korunmuş olan MAPK’ler, tek ve çok hücreli birçok ökaryotik organizmaların evrensel bir sinyal iletim yoludur ve bu biyokimyasal yolla dış çevresel uyarıcı anlamlı bir bilgiye dönüştürülür. Bitkilerde MAPK olaylar dizisi biyotik/abiyotik streslere tepki ve gelişim programıyla ilgili çeşitli olayları kapsayan biyolojik süreçlerin kontrol mekanizması gibi işlev görürler. Patojenisite faktörlerinin bitki tarafından tanınmasından sonra bitki savunma tepkimelerini harekete geçiren ilk sinyalizasyon olayları; reseptör-benzeri kinazların, kalsiyum-bağlı kinazların ve MAP kinazların fosforilasyonudur. MAPK kademeli olayları bitki stres ve/veya savunma hormonlarının biyosentezi ve sinyal bildirimi, reaktif oksijen türlerinin üretimi, stomaların kapanması, savunma genlerinin aktif hale geçmesi, fitoaleksin biyosentezi, hücre duvarının güçlenmesi ve aşırı duyarlılıkla ilgili hücre ölümleri gibi çeşitli savunma tepkimelerinde sinyalizasyon faktörleri olarak görev yaparlar. Hücre-yüzey ve/veya sitoplazmik reseptörlerce algılanan elisitörler/efektörler’in verdiği mesajlar kademeli olarak bir dizi MAPK-fosforilasyon yoluyla çoğaltılarak ilerideki substratlara ulaşır. Fosforile olan MAPK’ler böylece aktiflenmiş olurlar. MAPK dizisinin ileri aşamalarında yer alan substratlar, çeşitli proteinler/transkriptomlar da aktiflenen MAPK’lerle fosforile edilerek gen anlatımı, biyokimyasal ve fizyolojik düzeyde değişimler yaparak hücreyi manipule ederler. Böylece biyotik/abiyotik streslere uygun tepkiler gelişmeye başlar. MAPK modülleri her iki PTI/ETI immünite de sinyal elemanlarıdır. Ancak patojenisite faktörlerinin bitkilerce algılanmasından (ETI/PTI immünitede) sonra bitki savunmasında önemli roller üstlenen MAPK aktiflenmesi ETI immünitede, PTI savunmaya göre daha güçlü, yavaş, uzun süreli ve efektördeki değişimlere karşı daha esnek özelliklere sahiptir. ETI immünitede NLR moleküllerinin aktiflenmesi MAPK’lerin harekete geçmesine yol açar ancak MAPK’lerin nasıl etkinleştiği mekanizması henüz net değildir. Hücre yüzey reseptörleriyle teşvik edilen bitki PTI immünite ile MAPK’nin hızlı etkinleşme mekanizması daha iyi bilinmektedir. Bu nedenle ele alınan derlemede bitki immünitesindeki MAPK’lerin PTI immüniteye dahil olan bağlantı yollarına odaklanılmıştır.

Genetic and phenotypic attributes of splenic marginal zone lymphoma

AbstractSplenic marginal zone B-cell lymphoma (SMZL) is a heterogeneous clinico-biological entity. The clinical course is variable, multiple genes are mutated with no unifying mechanism, and essential regulatory pathways and surrounding microenvironments are diverse. We sought to clarify the heterogeneity of SMZL by resolving different subgroups and their underlying genomic abnormalities, pathway signatures, and microenvironment compositions to uncover biomarkers and therapeutic vulnerabilities. We studied 303 SMZL spleen samples collected through the IELSG46 multicenter international study (NCT02945319) by using a multiplatform approach. We carried out genetic and phenotypic analyses, defined self-organized signatures, validated the findings in independent primary tumor metadata and determined correlations with outcome data. We identified 2 prominent genetic clusters in SMZL, termed NNK (58% of cases, harboring NF-κB, NOTCH, and KLF2 modules) and DMT (32% of cases, with DNA-damage response, MAPK, and TLR modules). Genetic aberrations in multiple genes as well as cytogenetic and immunogenetic features distinguished NNK- from DMT-SMZLs. These genetic clusters not only have distinct underpinning biology, as judged by differences in gene-expression signatures, but also different outcomes, with inferior survival in NNK-SMZLs. Digital cytometry and in situ profiling segregated 2 basic types of SMZL immune microenvironments termed immune-suppressive SMZL (50% of cases, associated with inflammatory cells and immune checkpoint activation) and immune-silent SMZL (50% of cases, associated with an immune-excluded phenotype) with distinct mutational and clinical connotations. In summary, we propose a nosology of SMZL that can implement its classification and also aid in the development of rationally targeted treatments.

Clotrimazole-Induced Oxidative Stress Triggers Novel Yeast Pkc1-Independent Cell Wall Integrity MAPK Pathway Circuitry.

Azoles are one of the most widely used drugs to treat fungal infections. To further understand the fungal response to azoles, we analyzed the MAPK circuitry of the model yeast Saccharomyces cerevisiae that operates under treatment with these antifungals. Imidazoles, and particularly clotrimazole, trigger deeper changes in MAPK phosphorylation than triazoles, involving a reduction in signaling through the mating pathway and the activation of the MAPKs Hog1 and Slt2 from the High-Osmolarity Glycerol (HOG) and the Cell Wall Integrity (CWI) pathways, respectively. Clotrimazole treatment leads to actin aggregation, mitochondrial alteration, and oxidative stress, which is essential not only for the activation of both MAPKs, but also for the appearance of a low-mobility form of Slt2 caused by additional phosphorylation to that occurring at the conserved TEY activation motif. Clotrimazole-induced ROS production and Slt2 phosphorylation are linked to Tpk3-mediated PKA activity. Resistance to clotrimazole depends on HOG and CWI-pathway-mediated stress responses. However, Pkc1 and other proteins acting upstream in the pathway are not critical for the activation of the Slt2 MAPK module, suggesting a novel rewiring of signaling through the CWI pathway. We further show that the strong impact of azole treatment on MAPK signaling is conserved in other yeast species.

Aromatic Cytokinin Arabinosides Promote PAMP-like Responses and Positively Regulate Leaf Longevity.

Cytokinins are plant hormones with biological functions ranging from coordination of plant growth to the regulation of biotic and abiotic stress-related responses and senescence. The components of the plant immune system can learn from past elicitations by microbial pathogens and herbivores and adapt to new threats. It is known that plants can enter the primed state of enhanced defense induced by either natural or synthetic compounds. While the involvement of cytokinins in defense priming has been documented, no comprehensive model of their action has been provided to date. Here, we report the functional characterization of two aromatic cytokinin derivatives, 6-benzylaminopurine-9-arabinosides (BAPAs), 3-methoxy-BAPA and 3-hydroxy-BAPA, that proved to be effective in delaying senescence in detached leaves while having low interactions with the cytokinin pathway. An RNA-seq profiling study on Arabidopsis leaves treated with 3-methoxy-BAPA revealed that short and extended treatments with this compound shifted the transcriptional response markedly toward defense. Both treatments revealed upregulation of genes involved in processes associated with plant innate immunity such as cell wall remodeling and upregulation of specific MAP kinases, most importantly MPK11, which is a MAPK module involved in stress-related signaling during the pathogen-associated molecular patterns (PAMPs) response. In addition, elevated levels of JA and its metabolites, jasmonate/ethylene-driven upregulation of PLANT DEFENSIN 1.2 (PDF1.2) and other defensins, and also temporarily elevated levels of reactive oxygen species marked the plant response to 3-methoxy-BAPA treatment. Synergistic interactions were observed when plants were cotreated with 3-hydroxy-BAPA and the flagellin-derived bacterial PAMP peptide (flg22), leading to the enhanced expression of the PAMP-triggered immunity (PTI) marker gene FRK1. Our data collectively show that some BAPAs can sensitively prime the PTI responses in a low micromolar range of concentrations while having no observable negative effects on the overall fitness of the plant.

The MEK5-ERK5 Kinase Axis Controls Lipid Metabolism in Small-Cell Lung Cancer.

Small-cell lung cancer (SCLC) is an aggressive form of lung cancer with dismal survival rates. While kinases often play key roles driving tumorigenesis, there are strikingly few kinases known to promote the development of SCLC. Here, we investigated the contribution of the MAPK module MEK5-ERK5 to SCLC growth. MEK5 and ERK5 were required for optimal survival and expansion of SCLC cell lines in vitro and in vivo. Transcriptomics analyses identified a role for the MEK5-ERK5 axis in the metabolism of SCLC cells, including lipid metabolism. In-depth lipidomics analyses showed that loss of MEK5/ERK5 perturbs several lipid metabolism pathways, including the mevalonate pathway that controls cholesterol synthesis. Notably, depletion of MEK5/ERK5 sensitized SCLC cells to pharmacologic inhibition of the mevalonate pathway by statins. These data identify a new MEK5-ERK5-lipid metabolism axis that promotes the growth of SCLC. SIGNIFICANCE: This study is the first to investigate MEK5 and ERK5 in SCLC, linking the activity of these two kinases to the control of cell survival and lipid metabolism.

Stepwise signal transduction cascades under salt stress in leaves of wild barley (Hordeum spontaneum)

The present study aims at the use of transcriptomic data of wild barley (Hordeum spontaneum) under salt stress in detecting regulated metabolites and crosstalking signal transduction pathways that help plants withstand harsh conditions. The studied pathways involved those emphasizing the roles of phytohormones auxin and abscisic acid (ABA) in conferring stress tolerance and adaptation. Of which, tryptophan-core pathways include metabolites that trigger auxin-responsive genes towards downstream signal transduction cascades and better plant growth. Analysis of ‘MAPK signalling’ pathway indicated active participation of several MAPK modules in receiving and delivering signals under salt stress towards appropriate downstream biological decisions. The results indicated that one enriched MEKK1 module, e.g. MEKK1-MKK2-MPK4/6, and two MKK3 modules, e.g. MEKK17/18-MKK3-MPK1/2/7/14 and ?-MKK3-MPK8, in this wild plant can effectively participate in salt stress adaptation and tolerance as well as homeostasis of reactive oxygen species (ROS). ABA seems to be a main player in the leaves of H. spontaneum in triggering signal transduction via MAPK modules. MKK7 was shown to be repressed under salt stress. This MAPK disturbs normal production, signalling and distribution of auxin, thus, enforces the plant to perform better under salt stress. In conclusion, the present study addresses signal transduction pathways that might justify the ability of this wild plant to tolerate salt stress.

Mitogen-activated protein kinase 6 integrates phosphate and iron responses for indeterminate root growth in Arabidopsis thaliana.

A MAPK module, of which MPK6 kinase is an important component, is involved in the coordination of the responses to Pi and Fe in the primary root meristem of Arabidopsis thaliana. Phosphate (Pi) deficiency induces determinate primary root growth in Arabidopsis through cessation of cell division in the meristem, which is linked to an increased iron (Fe) accumulation. Here, we show that Mitogen-Activated Protein Kinase6 (MPK6) has a role in Arabidopsis primary root growth under low Pi stress. MPK6 activity is induced in roots in response to low Pi, and such induction is enhanced by Fe supplementation, suggesting an MPK6 role in coordinating Pi/Fe balance in mediating root growth. The differentiation of the root meristem induced by low Pi levels correlates with altered expression of auxin-inducible genes and auxin transporter levels via MPK6. Our results indicate a critical role of the MPK6 kinase in coordinating meristem cell activity to Pi and Fe availability for proper primary root growth.

The p38/HOG stress-activated protein kinase network couples growth to division in Candida albicans.

Cell size is a complex trait that responds to developmental and environmental cues. Quantitative size analysis of mutant strain collections disrupted for protein kinases and transcriptional regulators in the pathogenic yeast Candida albicans uncovered 66 genes that altered cell size, few of which overlapped with known size genes in the budding yeast Saccharomyces cerevisiae. A potent size regulator specific to C. albicans was the conserved p38/HOG MAPK module that mediates the osmostress response. Basal HOG activity inhibited the SBF G1/S transcription factor complex in a stress-independent fashion to delay the G1/S transition. The HOG network also governed ribosome biogenesis through the master transcriptional regulator Sfp1. Hog1 bound to the promoters and cognate transcription factors for ribosome biogenesis regulons and interacted genetically with the SBF G1/S machinery, and thereby directly linked cell growth and division. These results illuminate the evolutionary plasticity of size control and identify the HOG module as a nexus of cell cycle and growth regulation.

Quantifying the relative importance of experimental data points in parameter estimation

BackgroundOrdinary differential equations (ODEs) are often used to understand biological processes. Since ODE-based models usually contain many unknown parameters, parameter estimation is an important step toward deeper understanding of the process. Parameter estimation is often formulated as a least squares optimization problem, where all experimental data points are considered as equally important. However, this equal-weight formulation ignores the possibility of existence of relative importance among different data points, and may lead to misleading parameter estimation results. Therefore, we propose to introduce weights to account for the relative importance of different data points when formulating the least squares optimization problem. Each weight is defined by the uncertainty of one data point given the other data points. If one data point can be accurately inferred given the other data, the uncertainty of this data point is low and the importance of this data point is low. Whereas, if inferring one data point from the other data is almost impossible, it contains a huge uncertainty and carries more information for estimating parameters.ResultsG1/S transition model with 6 parameters and 12 parameters, and MAPK module with 14 parameters were used to test the weighted formulation. In each case, evenly spaced experimental data points were used. Weights calculated in these models showed similar patterns: high weights for data points in dynamic regions and low weights for data points in flat regions. We developed a sampling algorithm to evaluate the weighted formulation, and demonstrated that the weighted formulation reduced the redundancy in the data. For G1/S transition model with 12 parameters, we examined unevenly spaced experimental data points, strategically sampled to have more measurement points where the weights were relatively high, and fewer measurement points where the weights were relatively low. This analysis showed that the proposed weights can be used for designing measurement time points.ConclusionsGiving a different weight to each data point according to its relative importance compared to other data points is an effective method for improving robustness of parameter estimation by reducing the redundancy in the experimental data.

Mitogen activated protein kinase 6 and MAP kinase phosphatase 1 are involved in the response of Arabidopsis roots to L-glutamate.

The function and components of L-glutamate signaling pathways in plants have just begun to be elucidated. Here, using a combination of genetic and biochemical strategies, we demonstrated that a MAPK module is involved in the control of root developmental responses to this amino acid. Root system architecture plays an essential role in plant adaptation to biotic and abiotic factors via adjusting signal transduction and gene expression. L-Glutamate (L-Glu), an amino acid with neurotransmitter functions in animals, inhibits root growth, but the underlying genetic mechanisms are poorly understood. Through a combination of genetic analysis, in-gel kinase assays, detailed cell elongation and division measurements and confocal analysis of expression of auxin, quiescent center and stem cell niche related genes, the critical roles of L-Glu in primary root growth acting through the mitogen-activated protein kinase 6 (MPK6) and the dual specificity serine-threonine-tyrosine phosphatase MKP1 could be revealed. In-gel phosphorylation assays revealed a rapid and dose-dependent induction of MPK6 and MPK3 activities in wild-type Arabidopsis seedlings in response to L-Glu. Mutations in MPK6 or MKP1 reduced or increased root cell division and elongation in response to L-Glu, possibly modulating auxin transport and/or response, but in a PLETHORA1 and 2 independent manner. Our data highlight MPK6 and MKP1 as components of an L-Glu pathway linking the auxin response, and cell division for primary root growth.

Glucosamine stimulates pheromone-independent dimorphic transition in Cryptococcus neoformans by promoting Crz1 nuclear translocation.

Morphotype switch is a cellular response to external and internal cues. The Cryptococcus neoformans species complex can undergo morphological transitions between the yeast and the hypha form, and such morphological changes profoundly affect cryptococcal interaction with various hosts. Filamentation in Cryptococcus was historically considered a mating response towards pheromone. Recent studies indicate the existence of pheromone-independent signaling pathways but their identity or the effectors remain unknown. Here, we demonstrated that glucosamine stimulated the C. neoformans species complex to undergo self-filamentation. Glucosamine-stimulated filamentation was independent of the key components of the pheromone pathway, which is distinct from pheromone-elicited filamentation. Glucosamine stimulated self-filamentation in H99, a highly virulent serotype A clinical isolate and a widely used reference strain. Through a genetic screen of the deletion sets made in the H99 background, we found that Crz1, a transcription factor downstream of calcineurin, was essential for glucosamine-stimulated filamentation despite its dispensability for pheromone-mediated filamentation. Glucosamine promoted Crz1 translocation from the cytoplasm to the nucleus. Interestingly, multiple components of the high osmolality glycerol response (HOG) pathway, consisting of the phosphorelay system and some of the Hog1 MAPK module, acted as repressors of glucosamine-elicited filamentation through their calcineurin-opposing effect on Crz1’s nuclear translocation. Surprisingly, glucosamine-stimulated filamentation did not require Hog1 itself and was distinct from the conventional general stress response. The results demonstrate that Cryptococcus can resort to multiple genetic pathways for morphological transition in response to different stimuli. Given that the filamentous form attenuates cryptococcal virulence and is immune-stimulatory in mammalian models, the findings suggest that morphogenesis is a fertile ground for future investigation into novel means to compromise cryptococcal pathogenesis.

The integration of G\u03b2 and MAPK signaling cascade in zygote development

Cells respond to many signals with a limited number of signaling components. Heterotrimeric G proteins and MAPK cascades are universally used by eukaryotic cells to transduce signals in various developmental processes or stress responses by activating different effectors. MAPK cascade is integrated with G proteins by scaffold protein during plant immunity. However, the molecular relationship between G proteins and MAPK modules in plant development is still unclear. In this study, we demonstrate that Arabidopsis Gβ protein AGB1 interacts with MPK3 and 6, MKK4 and 5, as well as the regulatory domains of YODA (YDA), the upstream MEKK of MKK4/5. Remarkably, YDA interacts with the plasma membrane associated SHORT SUSPENSOR (SSP) through its N- and C-terminal region in vitro and in vivo. Additionally, genetic analysis shows that AGB1 functions together with MPK3/6 signaling cascade during the asymmetric division of the zygote. These data indicate that Gβ may function likely as a scaffold, through direct physical interaction with the components of the MPK signaling module in plant development. Our results provide new insights into the molecular functions of G protein and will advance the understanding of the complex mechanism of kinase signaling cascades.

ХАВДАР ЭСИЙН ҮЙЛ АЖИЛЛАГААНД JSAP (JNK/STRESS-ACTIVATED PROTEIN KINASE-ASSOCIATED PROTEIN) УУРГИЙН ОРОЛЦОО

JSAP1 and JSAP2 are structurally close related family proteins and originally have been identified as scaffold proteins of the JNK and p38 MAPK modules. The specificity of MAPK cascades is regulated, at least in part, by scaffold proteins, such as JSAPs[1-7]. Some studies showed [7-12] that JSAPs function as adaptor proteins which link cargoes to kinesin-1, the cellular cargo transporter along with microtubules. Also JSAPs regulate certain crucial neuronal processes, particularly axon elongation, branching and neurite outgrowth[13-22]. Interestingly, in recent studies it was reported that an elevated expression of JSAP2 protein in various cancers, including breast, colorectal cancer and hepatocellular carcinoma, might be proposed as a biomarker for diagnosis of cancers at early stage[25-28]. However, roles of JSAP in cancer cells and their underling molecular mechanisms are not known well at present. Within our project which aims to clarify potential roles of JSAPs in cancers, in the present study an overexpression of JSAPs in HeLa cells using lentiviral vectors were performed and immunocytochemical analyses focused on centrosomes at mitotic stage of dividing cells were done. In results, in HeLa dividing cells, which overexpress the wild type of JSAPs or their substitution mutant forms a multiple centrosome at mitotic stage of cells were found. However, in case of overexpression of the deletion mutant JSAP proteins in cancer cells a multi-centrosome abnormality were not observed, as well as in control cells.