After Effects CC 2015.3 is a brand new version of After Effects. It is not an update to CC 2015 as it might seem. It'd be better to think of it as CC 2016. You can even have CC 2015 and CC 2015.3 installed alongside each other just like you can have CC 2014 installed alongside the other versions.
So, you need the new version of Premiere Pro too. Or use the older version of AE with the older version of Premiere.
Remember, your CC subscription includes any version of any CC software you want from CS6 onward through CC, CC 2014, CC 2015, and CC 2015.x