Okay --- maybe THIS is finally it? Maybe this is the tool that can link all the phosphoproteomics data together into something that saves us from having to look up each and every one, or relying on that one "pathway analysis guru" that you might or might not be lucky enough to have at your work, or occasionally go rock climbing with? (I've been trying to figure out a social distancing rock climbing solution, to no avail....booooo....2020....booo.....)
I haven't test driven it yet, but a quick check of the figure above (what I highlighted) MAPK1/3 are definitely linked to the phosphorylations on Q15418. If those are linked to TP53 phosphorylation regulation, UniProt doesn't shout it out in the first page, but it seems very likely that they'd be linked by one of the many data sources that piNET is actively referencing!
The trick is filtering out the studies where people were obviously going for peak bagging (trying to grab bragging rights for the highest number of phosphorylation sites they could identify, something that was mistakenly thought to be cool for about 2 weeks one year long long ago, that we all universally agree is not at all cool to do now and was just an unfortunate mixup) but with some filtering capabilities in this software? This looks like an insanely powerful and useful new tool for our utility belts!