Add the langdalepl/gvfs-mtp package repository and update:
sudo add-apt-repository ppa:langdalepl/gvfs-mtp sudo apt-get update
Then upgrade the system and you should see some GVFS packages.
sudo apt-get upgrade
Once this finishes reboot your system and then plugin your Nexus 4 and it should work.
Ref: http://forum.xda-developers.com/nexus-4/general/mtp-support-ubuntu-12-04precise-nexus-4-t2330238