NEW YORK (AP) — JPMorgan Chase has appointed Matt Zames and Frank Bisignano as co-chief operating officers in a broad reshuffling of top management at the bank.

It was most visible change yet at the nation's largest bank, which is reeling from the fallout of a trading loss at one of its divisions that has ballooned to up to $5.8 billion from an initial estimate of $2 billion. The loss has prompted two congressional hearings and led to investigations from international regulators.

Zames' appointment is a big step up for the 41-year-old executive into the top-most ranks at the bank. Until the trading loss announced in May, Zames was co-head of global fixed income at the investment bank. He was recently named to replace the chief investment officer who oversaw the division where the loss occurred.