General Motors Co. on Thursday named Brian K. Sweeney, a 20-year company veteran, to head its Buick and GMC brands.

Sweeney replaces Michael Richards, who abruptly left the company on Dec. 10 after just eight days on the job. Sweeney, 42, is the latest in a string of appointments at the automaker, which has been undergoing a management shake-up under Chairman and CEO Edward Whitacre Jr.

Last week, the automaker appointed James Campbell to head its Chevrolet brand, its largest and most important brand, after the previous executive spent just five months on the job.

Buick is also a key brand for GM. The company is trying to erase Buick's stodgy image with more stylish cars and crossovers. Recent new launches include its top-selling Lacrosse sedan and its No. 2 Enclave crossover, which have been big hits.

Sweeney previously served as sales manager for Buick and GMC, working with dealers to sell cars and trucks. Jennifer Costabile, a Cadillac regional sales manager, was named to Sweeney's old post.