8.A.141. The Eros Chaperone Protein (Eros) Family In response to extracellular ATP, the purinergic receptor P2X7 mediates various biological processes, including phosphatidylserine (PtdSer) exposure, phospholipid scrambling, dye uptake, ion transport, and interleukin (IL)-1beta production. A transmembrane protein, 'Essential for reactive oxygen species' (Eros) is a necessary protein for P2X7 expression (Ryoden et al. 2020). An Eros-null mouse T cell line lost the ability to expose PtdSer, to scramble phospholipids, and to internalize a dye, YO-PRO-1, and Ca²⁺. The eros-null mutation abolished the ability of macrophages to secrete IL-1beta in response to ATP. Eros is localized to the endoplasmic reticulum and functions as a chaperone for NADPH oxidase components. Similarly, Eros at the endoplasmic reticulum transiently associates with P2X7 to promote the formation of a stable homotrimeric complex of P2X7. Thus, Eros acts as a chaperone not only for NADPH oxidase, but also for P2X7, and it contributes to the innate immune reaction (Ryoden et al. 2020).
References:
Ryoden, Y., T. Fujii, K. Segawa, and S. Nagata. (2020). Functional Expression of the P2X7 ATP Receptor Requires Eros. J Immunol 204: 559-568.
Examples:
TC#	Name	Organismal Type	Example
8.A.141.1.1	Eros chaparone protein of 468 aas and one N-terminal TMS. In response to extracellular ATP, the purinergic receptor P2X7 (1.A.7.1.3) mediates various biological processes, including phosphatidylserine (PtdSer) exposure, phospholipid scrambling, dye uptake, ion transport, and IL-1beta production. Eros in mice is absolutely required for P2X7 function in all of these capacities. It probably functions as a chaparone protein for the insertion and assembly of this system as well as others (Ryoden et al. 2020).		Eros of Homo sapiens

8.A.141.1.2	Endoplasmic reticulum oxidoreductins 2, Ero2, of 479 aas and 1 N-terminal TMS.		*Ero2 of Arabidopsis thaliana* (Mouse-ear cress)**

8.A.141.1.3	Endoplasmic reticulum oxidoreductin, putative of 469 aas and 2 TMSs, N- and C-terminal, with up to four additional possible TMSs, hydrophobic peaks that may or may not be TMSs.		*Eros of Plasmodium vinckei* petteri**

8.A.141.1.4	AERO1 of 333 aas and at least two TMSs, N- and C-terminal, and possibly more in between, based on hydrophathy plots.		AERO1 of Enterocytozoon hepatopenaei

8.A.141.1.5	Uncharacterized protein of 295 aas with 2 TMSs, N- and C-terminal. Possibly oxidoreductase, acting on a sulfur group of donors and a disulfide as acceptor (InterPro).		UP of Emiliania huxleyi (Pontosphaera huxleyi)