Prism ICommand from region to shell

I trying to create some regions, and in one of that regions, I have button "login" and ICommand Login property it is bound to. So I want to subscribe to this Login from shell.

I tried PubSubEvent, but I also need CanExecute method.

Another solution I have found, is to use static class with static commands. This I think is not a good pattern.

How to do this right from pattern perspective?

EDIT 1

To assign a region, I invoke this in constractor of shell's view model:

regionManager.RegisterViewWithRegion("MainContent", typeof(LoginArea));

And in view I use this ViewModelLocator.AutoWireViewModel="True", so I could not inject my shell's view model to subscribe events to it.