Last April General Motors made some structural changes to its brand operations, consolidating a lot of redundant work into a single channel. As part of that change, Mark McNabb was appointed head of Cadillac, Hummer and Saab as chief of GM's premium division. Things have changed at GM since then, to be sure, and now McNabb has resigned his post.

Effective June 1, McNabb will leave GM to 'pursue other opportunities', reports Automotive News. Stephen J. Hill will fill in as interim chief.

Hill is already familiar with the brand's operations, as he has been general sales manager of GM's premium division since 2008. He'll also be continuing in that position while taking over McNabb's duties.

Before serving as the head of Cadillac, McNabb held positions as senior vice president of sales and marketing at Nissan/Infiniti and head of marketing and vice preseident of sales at Mercedes-Benz USA.