It is advised that you hold off on editing a PPP (project protected profile) until consulting the project. This profile is not PPP and can be edited by anyone, that's what collaboration is all about. In most cases, a profile is only PPP if there is some sort of issue like erroneous parents that people keep attaching, removing, attaching, removing...
That being said, it is only polite to notify the existing profile managers of any changes you are making. This can be done by sending a PM, leaving a message on the profile page, or filling out the little box explaining your changes. Sometimes I leave the changes I want to make, with the source, as a message on the profile.