The metabolic clearance in the early produced dhCer could influence cell fate, as its accumulation in response to fenretinide therapy was shown to induce cell toxicity once the glucosylation pathway was inhibited . In our model, the time program of formation of metabolites suggests that transformation of dhCer into dhSM is favored above glucosylation. On this regard, it will have to be taken into account that though dhCer neo synthesis occurs in the ER, its glucosylation and metabolization into dhSM occur in other compartments. The transport to internet sites of dhSM synthesis calls for the Cer transporter protein CERT, whereas transport on the Golgi for glucosylation is CERT independent. Hanada and co workers demonstrated that dhCer are less efficiently transported by CERT than Cer . In addition, in our technique, such a transport, that is ATP dependent, takes place in temporarily arrested autophagic cells, in which power consuming processes are turned off. This raises the chance that the accumulated dhCer may very well be trafficked for dhSM synthesis by an ATP independent strategy.
We also demonstrate that dhCer desaturase inhibition brings about ER stress. It is actually doable that newly synthesized dhCer accumulates at first in the ER and activates ER pressure sensors. The activation of pressure signaling cascades could possibly involve alterations in membrane biophysical properties, since it has become published that dhCer and dhSPLs enrichment greatly reduce membrane permeability . We observed that autophagy promotion was related with Beta-catenin inhibitors the splicing of Xbp, a identified pro survival gene expression promoter activated within the UPR ER strain induced response. We speculate the observed two phases activation of Xbp might rely on the rapid response, straight mediated by de novo synthesized dhCer , whereas the late activation of Xbp may perhaps entail a response to other mechanisms linked to cell metabolic process and anxiety adaptation. Moreover, we observed ser phosphorylation of eIF , stopping protein translation initiation.
This latter obtaining explains the observed modulation of cyclin D as well as prompt induction of autophagy like a survival system to encounter ER strain and reduced protein synthesis. Literature evidences recognize autophagy as an extension within the UPR response, supporting cycle arrest Panobinostat . In our model, whereas autophagy and ER tension are still happening at very long time right after XM therapy , the G S transition is delayed only for a couple of hrs, in coincidence with the highest enhance of dhCers above the preliminary values with the time of XM administration. Nevertheless, handled cells exhibit a decreased proliferation rate up to h, suggesting a switch to a slow development phenotype.