Natural Mutation in Naked Mole-Rat UCP1 Refutes Importance of the Histidine Pair Motif for Proton Conductance and Thermogenesis

Aim

Uncoupling protein 1 (UCP1) is the crucial protein for non-shivering thermogenesis in placental mammals, but the molecular mechanism of thermogenic proton transport is still unknown. Its histidine pair motif (H145 and H147) has been claimed as a critical element for proton translocation, leading to the paradigmatic “cofactor model” of the UCP1 thermogenic mechanism. The histidine pair motif is mutated (H145Q) in the naked mole-rat (NMR, Heterocephalus glaber) UCP1, suggesting disrupted thermogenic function in line with NMR's poor thermoregulatory abilities. Here, we investigated the functionality NMR versus mouse UCP1 to scrutinized the importance of the histidine pair motif.

Methods

Respiratory analyses for UCP1 function were performed in isolated brown adipose tissue mitochondria from NMR and mouse. The histidine pair motif of NMR UCP1 was manipulated through mutations, ectopically overexpressed in HEK293 cells and subjected to plate-based respirometry for functional comparison.

Results

Isolated BAT mitochondria of NMRs display guanosine diphosphate-sensitive respiration, indicative of thermogenically competent UCP1. Overexpressed wildtype NMR UCP1 demonstrates proton leak activity comparable to mouse UCP1. Neither restoration of the histidine pair motif nor full ablation of the motif through a double mutation affects UCP1-dependent respiration.

Conclusions

The UCP1 variant of the NMR, a warm-adapted fossorial species, excludes the histidine pair motif as crucial for UCP1 thermogenic function. Collectively, we show that functional investigation into natural sequence variation of UCP1 not only casts new light on the thermophysiology of NMRs but also represents a powerful tool to delineate structure-function relationships underlying the enigmatic thermogenic proton transport of UCP1.