Cristae Membrane Dynamics – A Paradigm Change

Mitochondria are dynamic organelles that have essential metabolic and regulatory functions. Earlier studies using electron microscopy (EM) revealed an immense diversity in the architecture of cristae – infoldings of the mitochondrial inner membrane (IM) – in different cells, tissues, bioenergetic and metabolic conditions, and during apoptosis. However, cristae were considered to be largely static entities. Recently, advanced super-resolution techniques have revealed that cristae are independent bioenergetic units that are highly dynamic and remodel on a timescale of seconds. These advances, coupled with mechanistic and structural studies on key molecular players, such as the MICOS (mitochondrial contact site and cristae organizing system) complex and the dynamin-like GTPase OPA1, have changed our view on mitochondria in a fundamental way. We summarize these recent findings and discuss their functional implications.