NEW YORK ( TheStreet) -- Shares of Best Buy ( BBY) rose Tuesday after the company announced that its CEO has resigned. Best Buy CEO Brian Dunn said Tuesday he is leaving the company. Director Mike Mikan is taking over as interim CEO while Best Buy searches for Dunn's replacement. "There were no disagreements between Mr. Dunn and the company on any matter relating to operations, financial controls, policies or procedures," a Best Buy statement said. "There was mutual agreement that it was time for new leadership to address the challenges that face the company." Mikan was previously chief financial officer and executive vice president at UnitedHealth Group ( UNH). Best Buy announced on March 30 that it plans to close 50 U.S. stores in 2013 and will cut costs by $800 million by fiscal year 2015. Shares of Best Buy rose 2.91% to $23.31 in early trading Tuesday. The stock has risen 20 cents, or 0.86%, year to date. TheStreet Ratings gives Best Buy a C grade and hold rating.