Abstract <p><b>Objective:</b> The protein p42^IP4/centaurin-α1/ADAP1 is a neuronal protein associated with mitochondria, whose presumed role is linked to the regulation of inner membrane permeability. This study investigated the effects of ADAP1 overexpression and its ligand inositol 1,3,4,5-tetrakisphosphate (IP₄) on bioenergetics and calcium homeostasis in mitochondria isolated from neuronal N2a cells and non-neuronal CHO cells. ADAP1 exerted a pronounced and cell-type-specific impact on key functional parameters. <b>Material and Methods:</b> Mitochondria were isolated from wild-type N2a and CHO cells and those transfected with p42^IP4/centaurin-α1/ADAP1. Respiratory activity, mitochondrial Ca²⁺ uptake rate, and Ca²⁺ capacity were assessed. <b>Results:</b> In mitochondria isolated from neuronal (N2a) cells, ADAP1 overexpression reduced the efficiency of oxidative phosphorylation, with decreased respiratory control and uncoupled respiration rate (Vu). Concurrently, there was a significant reduction in Ca²⁺ capacity, which determines mitochondrial resistance to permeability transition pore (mPTP) opening, and the ligand IP₄ potentiated this effect. In non-neuronal mitochondria (CHO), a two-fold impairment of respiratory coupling was observed; however, their Ca²⁺ capacity increased, whereas IP₄ addition reduced Ca²⁺ capacity in this model. Thus, ADAP1 acts as a key context-dependent modulator of mitochondrial function. <b>Conclusion:</b> The findings, particularly the lowered threshold for Ca²⁺-induced mPTP opening in neuronal mitochondria, support the hypothesis that this protein serves as a regulator influencing inner membrane ionic conductance and thereby integrating mitochondrial energy status with stress resilience.</p>