Table 1.

Summary of Selenoproteins

Selenoprotein	Abbreviation(s)	Function and significance
Cytosolic glutathione peroxidase	GPX1	GPX1 knockout is more suseptible to oxidative challenge. Overexpression of GPX1 increases risk of diabetes.
Gastrointestinal glutathione peroxidase	GPX2	GPX1/GPX2 double knockout mice develop intestinal cancer, one allele of GPX2 added back confers protection.
Plasma glutathione peroxidase	GPX3	Important for cardiovascular protection, perhaps through modulation of nitrous oxide levels; antioxidant in thyroid gland.
Phosholipid hydroperoxide glutathione peroxidase	GPX4	Genetic deletion is embryonic lethal; GPX4 acts as crucial antioxidant, and sensor of oxidative stress and proapoptotic signals.
Olfactory glutathione peroxidase	GPX6	Importance unknown.
Thioredoxin reductase type I	TXNRD1, TrxR1, TR1	Localized to cytoplasm and nucleus. Genetic deletion is embryonic lethal.
Thioredoxin reductase type II	TXNRD2, TrxR2, TR3	Localized to mitochondria. Genetic deletion is embryonic lethal.
Thioredoxin reductase type III	TXNRD3, TRxR3, TR2, TGR	Testes-specific expression.
Deiodinase type I	D1, DIO1	Important for systemic active thyroid hormone levels.
Deiodinase type II	D2, DIO2	Important for local active thyroid hormone levels.
Deiodinase type III	D3, DIO3	Inactivates thyroid hormone.
Selenoprotein H	SELH	Nuclear localization, involved in transcription. Essential for viability and antioxidant defense in Drosophila.
Selenoprotein I	SELI, hEPT1	Possibly involved in phospholipid biosynthesis.
Selenoprotein K	SELK	Transmembrane protein localized to endoplasmic reticulum and involved in calcium flux in immune cells.
Selenoprotein M, Selenoprotein 15	SELM, SEP15	Thiol-disulfide oxidoreductases localized to endoplasmic reticulum. Possibly involved in protein-folding.
Selenoprotein N	SELN, SEPN1, SepN	Potential role in early muscle formation; involved in RyR-related calcium mobilization from ER; mutations lead to multiminicore disease and other myopathies.
Selenoprotein O	SELO	Contains a Cys-X-X-Sec motif suggestive of redox function, but importance remains unknown.
Selenoprotein P	SELP, SEPP	Selenium transport to brain and testes—SELP knockout leads to neurological problems and male sterility. SELP also functions as intracellular antioxidant in phagocytes.
Selenoprotein R	SELR, MsrB1	Functions as a methionine sulfoxide reductase and SELR knockouts show mild damage to oxidative insult.
Selenoprotein S	SELS, SEPS1, SELENOS, VIMP	Transmembrane protein found in plasma membrane and endoplasmic reticulum. May be involved in ER stress.
Selenoprotein T	SELT	Endoplasmic reticulum protein involved in calcium mobilization.
Selenoprotein V	SELV	Testes-specific expression.
Selenoprotein W	SELW, SEPW1	Putative antioxidant role, perhaps important in muscle growth.
Selenophosphate synthetase	SPS2	Involved in synthesis of all selenoproteins, including itself.