Ecto-F1-ATPase: A moonlighting protein complex and an unexpected apoA-I receptor

Table 2 Ligands and roles of Ecto-F₁-ATPase

Cells/tissues	Ligands	Proposed roles	Ref.
K562, A549, Raji	?	NK/LAK-mediated tumor cell lysis	[38]
HUVEC	Angiostatin HDL/apoA-I	Cell survival through ATP production	[40,60,66]
	FC6	Cell survival through purinergic receptor activation
		Control of blood pressure
Hepatocytes	HDL/apoA-I	HDL endocytosis	[30]
3T3-L1, HaCat	?	Cell survival	[41,43]
Tumor cells	Vγ9/Vδ2 TCR, apoA-I, MHC-I	Tumor cell recognition by Vγ9/Vδ2 T cells/presentation of phosphoantigens	[31,33,46,67]
Tonsils (mouse)	Enterostatin	Food intake regulation	[44]
Neurons	APP, Amyloid β-peptide	Synaptic plasticity regulation	[45]

Major roles of Ecto-F₁-ATPase described in the literature, as well as ligands involved, are summarized here. MHC-I: Major histocompatibility complex class I; NK: Natural killer; LAK: Lymphokine activated killer; HDL: High density lipoprotein; apoA-I: Apolipoprotein A-I; FC6: Coupling factor 6; ATP: Adenosine triphosphate; APP: Amyloid precursor protein. Cells/tissues are of human origin unless otherwise noted. K562: Erythroleukemia; A549: Lung adenocarcinoma; Raji: Burkitt’s lymphoma; HUVEC: Human umbilical vein endothelial cells; 3T3-L1: Murine fibroblasts (differentiated into adipocytes); HaCat: Immortalized human keratinocytes.