One of Sina’s biggest shareholders is launching a proxy fight with the Chinese internet company, calling for measures it says will unlock value including a potential sale of itself or its big stake in wildly popular microblog service Weibo Corp, The Wall Street Journal reports. Aristeia Capital, a hedge fund with about $3 billion in assets, has proposed a range of options to address what it calls a persistent discount to Sina’s underlying value – especially considering its stake in Weibo. The fund is seeking changes that would reduce the valuation gap between Sina and Weibo, the Twitter-like firm in which Sina holds a stake of about 46%. Sina’s market value, which comprises its own operations plus the stake in Weibo, was about $8.2 billion as of Monday’s close – which is less than the market value of its stake in Weibo alone. Weibo’s market capitalization is about $22.9 billion. Both companies are listed in the US.