Market Movers Today: General Mills, Inc. (GIS), Prothena Corporation PLC (PRTA), Twitter Inc (TWTR), Southwest Airlines Co (LUV), and More

General Mills, Inc. (NYSE:GIS) (The Motley Fool)
What happened: Shares of General Mills, Inc. (NYSE:GIS) were tumbling today after the diversified food-maker posted third-quarter earnings and lowered its full-year forecast due to higher freight and commodity costs. As a result, the Cheerios-maker was down 9.9% as of 10:52 a.m. EDT. So what: The parent of brands including Yoplait, Nature Valley, Haagen-Dazs, and Annie’s said overall sales increased 2.3% in the period to $3.88 billion, which topped estimates of $3.78 billion.

Prothena Corporation PLC (NASDAQ:PRTA) (Benzinga)
Prothena Corporation plc rose 12.4 percent to $38.051 after the late-stage clinical biotech company announced a partnership with Celgene Corporation to develop therapies for a broad range of neurodegenerative diseases.

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Twitter Inc (NYSE:TWTR) (CNBC)
Twitter shares soared Wednesday after posting their worst session in over two years on Tuesday, and some traders are betting on more gains ahead. Shares of the popular social media company were up 5 percent early Wednesday. They had plunged 10 percent on Tuesday following reports that the company could face new regulation abroad. The social media space has been under pressure this week amid growing investor skepticism over Facebook’s data-sharing scandal.

Proteostasis Therapeutics Inc (NASDAQ:PTI) (MarketWatch)
Proteostasis Therapeutics Inc. PTI, +4.46% shares rose 14.2% in premarket trade Wednesday after the company said it won’t proceed with an equity offering due to “market conditions.” The decision followed the company’s stock being shorted by Kerrisdale Capital, betting that the stock would fall, and which caused shares to tank 26.2% on Tuesday. Proteostasis had previously planned to offer 9 million shares in a public offering announced on March 19.