Table 2.

Consequences of sideroflexins (SFXN) deficiency on the electron transport chain (ETC) complexes.

SFXN	Model	Complex	Data	Reference
SFXN1	HEK SFXN1 KO cells HeLa SFXN1 KO cells	CI	No significant loss of activity SDHB ↓	Acoba et al. 2020 [16]
		CII	No significant loss of activity UQCRC2 ↓↓ UQCRFS1 ↓↓
		CIII	Cytochrome b ↓↓↓ Significant loss of activity Reduced levels of CIII2 and CIII2-CIV respiratory complexes
SFXN2	HEK SFXN2 KO cells	CI CII-CIII CIV	No significant loss of activity Significant loss of activity Significant loss of activity	Mon et al. 2019 [9]
SFXN3	SFXN3 KO mouse	CI, CIV	No significant loss of activity	Amorim et al. 2017 [45]
SFXN4	Primary fibroblasts from two individuals with SFXN4 mutations	CI + CIII	Decreased activity	Hildick-Smith et al. 2013 [19]
	SFXN4 KD zebrafish	CI CI + CIII	Decreased activity	Sofou et al. 2019 [30]
	K562 SFXN4 KO cells	CI CII CIII CIV	NDUFB8 ↓ SDHB ↓ UQCRC2 ↓ COX2 ↓	Paul et al. 2019 [31]
SFXN5			N.A. 1

↓ indicates decreased levels of respiratory complexes subunits (↓ low, ↓↓ medium, ↓↓↓ high); ¹ N.A.: Not addressed.