Detailing the ultrastructure’s increase of prion protein in pancreatic adenocarcinoma

BACKGROUND Recent evidences have shown a relationship between prion protein(PrPc)expression and pancreatic ductal adenocarcinoma(PDAC).Indeed,PrPc could be one of the markers explaining the aggressiveness of this tumor.However,studies investigating the specific compartmentalization of increased PrPc expression within PDAC cells are lacking,as well as a correlation between ultrastructural evidence,ultrastructural morphometry of PrPc protein and clinical data.These data,as well as the quantitative stoichiometry of this protein detected by immuno-gold,provide a significant advancement in understanding the biology of disease and the outcome of surgical resection.AIM To analyze quantitative stoichiometry and compartmentalization of PrPc in PDAC cells and to correlate its presence with prognostic data METHODS Between June 2018 and December 2020,samples from pancreatic tissues of 45 patients treated with pancreatic resection for a preoperative suspicion of PDAC at our Institution were collected.When the frozen section excluded a PDAC diagnosis,or the nodules were too small for adequate sampling,patients were ruled out from the present study.Western blotting was used to detect,quantify and compare the expression of PrPc in PDAC and control tissues,such as those of non-affected neighboring pancreatic tissue of the same patient.To quantify the increase of PrPc and to detect the subcellular compartmentalization of PrPc within PDAC cells,immuno-gold stoichiometry within specific cell compartments was analyzed with electron microscopy.Finally,an analysis of quantitative PrPc expression according to prognostic data,such as cancer stage,recurrence of the disease at 12 mo after surgery and recurrence during adjuvant chemotherapy was made.RESULTS The amount of PrPc within specimen from 38 out of 45 patients was determined by semi-quantitative analysis by using Western blotting,which indicates that PrPc increases almost three-fold in tumor pancreatic tissue compared with healthy pancreatic regions[242.41±28.36 optical density(OD)vs 95±17.40 OD,P<0.0001].Quantitative morphometry carried out by using immuno-gold detection at transmission electron microscopy confirms an increased PrPc expression in PDAC ductal cells of all patients and allows to detect a specific compartmentalization of PrPc within tumor cells.In particular,the number of immuno-gold particles of PrPc was significantly higher in PDAC cells respect to controls,when considering the whole cell(19.8±0.79 particles vs 9.44±0.45,P<0.0001).Remarkably,considering PDAC cells,the increase of PrPc was higher in the nucleus than cytosol of tumor cells,which indicates a shift in PrPc compartmentalization within tumor cells.In fact,the increase of immuno-gold within nuclear compartment exceeds at large the augment of PrPc which was detected in the cytosol(nucleus:12.88±0.59 particles vs 5.12±0.32,P<0.0001;cytosol:7.74.±0.44 particles vs 4.3±0.24,P<0.0001).RESULTS In order to analyze the prognostic impact of PrPc,we found a correlation between PrPc expression and cancer stage according to pathology results,with a significantly higher expression of PrPc for advanced stages.Moreover,24 patients with a mean follow-up of 16.8 mo were considered.Immuno-blot analysis revealed a significantly higher expression of PrPc in patients with disease recurrence at 12 mo after radical surgery(360.71±69.01 OD vs 170.23±23.06 OD,P=0.023),also in the subgroup of patients treated with adjuvant CT(368.36±79.26 OD in the recurrence group vs 162.86±24.16 OD,P=0.028),which indicates a correlation with a higher chemo-resistance.CONCLUSION Expression of PrPc is significantly higher in PDAC cells compared with control,with the protein mainly placed in the nucleus.Preliminary clinical data confirm the correlation with a poorer prognosis.

Phase separation in plants:New insights into cellular compartmentalization

A fundamental challenge for cells is how to coordinate various biochemical reactions in space and time. To achieve spatiotemporal control, cells have developed organelles that are surrounded by lipid bilayer membranes. Further, membraneless compartmentalization, a process induced by dynamic physical association of biomolecules through phase transition offers another efficient mechanism for intracellular organization. While our understanding of phase separation was predominantly dependent on yeast and animal models, recent findings have provided compelling evidence for emerging roles of phase separation in plants. In this review, we first provide an overview of the current knowledge of phase separation, including its definition, biophysical principles, molecular features and regulatory mechanisms. Then we summarize plant-specific phase separation phenomena and describe their functions in plant biological processes in great detail. Moreover, we propose that phase separation is an evolutionarily conserved and efficient mechanism for cellular compartmentalization which allows for distinct metabolic processes and signaling pathways, and is especially beneficial for the sessile lifestyle of plants to quickly and efficiently respond to the changing environment.

Metabolism, signaling, and transport of jasmonates

Biosynthesis/metabolism,perception/signaling,and transport are three essential aspects of the actions of phytohormones.Jasmonates(JAs),including jasmonic acid(JA)and related oxylipins,are implicated in the regulation of a range of ecological interactions,as well as developmental programs to integrate these interactions.Jasmonoyl-isoleucine(JA-Ile)is the most bioactive JAs,and perception of JA-Ile by its coreceptor,the Skp1-Cullin1-F-box-type(SCF)protein ubiquitin ligase complex SCF^(COI1)-JAZ,in the nucleus derepresses the transcriptional repression of target genes.The biosynthesis and metabolism of JAs occur in the plastid,peroxisome,cytosol,endoplasmic reticulum,and vacuole,whereas sensing of JA-Ile levels occurs in the nucleus.It is increasingly apparent that a number of transporters,particularly members of the jasmonates transporter(JAT)family,located at endomembranes as well as the plasma membrane,constitute a network for modulating and coordinating the metabolic flux and signaling of JAs.In this review,we discuss recent advances in the metabolism,signaling,and especially the transport of JAs,focusing on intracellular compartmentation of these processes.The roles of transporter-mediated cell-cell transport in driving long-distance transport and signaling of JAs are also discussed.