Jamie Dimon, Chief Executive of JPMorgan Chase & Co. (NYSE:JPM), has lost another executive in his inner circle. Barry Zubrow, Head of Corporate and Regulatory Affairs at the investment bank, will depart from his position at the end of the year.

Yesterday, the former CEO of the company came out in support of Jamie Dimon. The company has seen several changes at the top in recent months, including the selection of a new CIO.

Jamie Dimon

Zubrow served as Chief Risk Officer at the company, until earlier this year, and was a key member of the team that Dimon trusted to lead JPMorgan Chase & Co. (NYSE:JPM) through the financial crisis and beyond. Zubrow is just the latest in a series of senior executives to leave the company in recent years. He joined the firm in 2007 from Goldman Sachs Group, Inc.(NYSE:GS).

In the last thirty six months six senior executives have left the company. All were members of Jamie Dimon’s “Operating Committee”, a group of the executive’s most trusted advisers. That group led JPMorgan Chase & Co. (NYSE:JPM) to success, while the rest of the financial world collapsed around it.

The largest investment bank in the world maneuvered through the financial crisis like no other, swallowing up failing institutions as they fell, all under the purview of the operating committee.

The company was rocked over the Summer, by the disclosure of billions of dollars in losses from trades originating in the company’s London office. Those trades have put the bank on the radar of several of the most prominent regulators in the United States.

One of the country’s foremost regulators, the Senate Permanent Subcommittee on Investigations, has questioned several of the top executives in the firm, since the losing trades came to light. The exact magnitude of the losses from the trades, and the culpability of their execution, has yet to be fully established.

Despite this, and the recent departures from the company, Dimon has been determined in his effort to put the mistakes of the company into the past. Dimon’s tenure at the head of the company, which began in 2005, has been celebrated by investors and analysts alike.

Shares in JPMorgan Chase & Co. (NYSE:JPM) have risen by more than 30% in the year to date, despite massive losses, owing to the bad trades in London. The company appears to be on firm footing, and investors still trust in the expertise of Dimon.

Despite losing some of his most trusted colleagues, Dimon seems uniquely focused on JPMorgan’s future. According to the Wall Street Journal, sources familiar with the matter say that the executive expects to spend several more years at the head of the company.

The full letter of resignation from Barry Zubrow is available below via the Wall Street Journal. The full text of that paper’s article on the resignation is here, including a response letter from James Dimon himself.