Twitter-like messaging service Weibo Corp filed on Friday to raise $500 million via a U.S. initial public offering, as Chinese companies flock to the American market in record numbers to take advantage of soaring valuations. Weibo, owned by Sina Corp, becomes the latest Chinese Internet giant to tap U.S. markets, following on the heels of search service Baidu and its own corporate parent. Alibaba, which owns a stake in Weibo, is expected to raise about $15 billion in New York this year, in the highest-profile Internet IPO since Facebooks in 2012.