what happens when control of platinum angel switches?

[Leafy]

what happens when the control of a platinum angel switches to another player, for example because of mind control?

[Arix]

Exactly the same thing that happens whenever anything changes control.

[Leafy]

i mean when I am at less than 0 life

[Kenji]

Assuming that it was previously your Platinum Angel, and you lost control of it?

State-based actions see that your life is at 0 or below, and you lose the game. As this is a state-based action, it takes place before any player receives priority. If you don't want to lose the game, you would need to get your life above 0 before losing control of Platinum Angel, or somehow keep Platinum Angel from leaving your control at all.