Figure 4.

Model for MICU1 and MICU2 regulation of uniporter physiology.

1. In WT cells at low external [Ca²⁺] below threshold, MICU1 and MICU2 inhibit Ca²⁺ transport (left). When [Ca²⁺] exceeds threshold, uniporter inhibition is removed and Ca²⁺ transport proceeds (right).
2. MICU1 KO cells have unregulated Ca²⁺ transport, resulting in uptake even at low [Ca²⁺] (left); MICU2 KO cells exhibit Ca²⁺ transport at the low [Ca²⁺] depicted (right).
3. Cells expressing either MICU1^EFmut or MICU2^EFmut lack Ca²⁺ transport because Ca²⁺ is unable to relieve MICU1/2 inhibition of the uniporter, regardless of concentration.