(CNN) — Bill Gates is stepping down from the boards of Microsoft and Berkshire Hathaway. In a press release Friday, Microsoft announced that its 64-year-old co-founder was leaving its board to "dedicate more time to his philanthropic priorities." "It's been a tremendous honor and privilege to have worked with and learned from Bill over the years," Mirosoft CEO Satya Nadella said in a written statement. "Microsoft will continue to benefit from Bill's ongoing technical passion and advice to drive our products and services forward. I am grateful for Bill's friendship and look forward to continuing to work alongside him to realize our mission to empower every person and every organization on the planet to achieve more." Gates will continue serving as technology adviser to Nadella and other Microsoft leaders, the company said. Separately in an SEC filing, Berkshire Hathaway said former American Express CEO Kenneth Chenault would replace Gates, who has served on Berkshire's board since 2004.