Prostaglandin-endoperoxide synthase 1 splice variant (COX-3) (COX-3)

Prostaglandin-endoperoxide synthase 1 splice variant, commonly known as COX-3, is an isoform of the COX-1 enzyme (PTGS1) characterized by the retention of intron 1 in its mRNA sequence (Simmons et al., 2002). It is primarily expressed in the central nervous system, particularly within the cerebral cortex and heart, and was famously proposed as the elusive central target for acetaminophen (paracetamol) and other antipyretic analgesics (Chandrasekharan et al., 2002). Unlike the traditional COX-1 and COX-2 isoforms, COX-3 exhibits a unique sensitivity to acetaminophen at therapeutic concentrations, which helps explain the drug's potent analgesic and antipyretic effects despite its weak peripheral anti-inflammatory activity (Botting, 2006). However, the functional relevance of COX-3 in humans is a subject of significant debate because the human PTGS1 gene contains a 94-base pair intron 1, which induces a frameshift mutation that may result in a non-functional protein or a truncated variant (NIH, 2024). Despite these species-specific genomic differences, the study of COX-3 remains critical for understanding the central mechanisms of pain and fever regulation and for the development of novel centrally-acting analgesics. Drugs such as dipyrone and phenacetin also interact with this variant, further supporting its role in mediating the effects of non-NSAID analgesics (PubMed, 2023).

Other names

COX-3COX-1bCOX-1vProstaglandin G/H synthase 1 variantPTGS1 variant 1Cyclooxygenase-3

Inhibition of prostaglandin synthesis, specifically PGE2, within the central nervous system to mediate analgesic and antipyretic effects.