Why not just import the PPro project mMP4is not a good idea at all.
To follow on with Wade's suggestion...
There are lots of ways to get movies and projects and other things back and forth between After Effects and Premiere Pro. This page outlines them:
If you must render and export a movie out of one application to bring it into another, there is a very basic piece of video workflow advice that you need to keep in mind (which applies to _all_ video software, not just After Effects and Premiere Pro):
If you're creating a movie to be used in the next step of a post-production pipeline, you _never_ want to use a format that does lossy compression. You either use no compression or (preferable) lossless compression. Examples of codecs that provide lossless compression are the Animation codec and PNG codec at the highest quality settings; these can be used in a QuickTime container, for example. Never compress a movie with lossy compression except at the very end of your pipeline, when you're creating the final movie for distribution.
MP4 (MPEG-4) is a lossy codec. The quality loss is acceptable for the last stage in the pipeline, but it's not acceptable for an intermediate file.