| Property | Summary |
|---|---|
| Gene name | **tax-4** (also known historically as abnormal chemotaxis protein 4) (pqac-00000025, pqac-00000040) |
| Protein name | Cyclic nucleotide-gated channel TAX-4 (CNG channel subunit) (pqac-00000006, pqac-00000017) |
| UniProt accession | **Q03611** |
| Organism | *Caenorhabditis elegans* (pqac-00000006, pqac-00000017) |
| Protein type | Cyclic nucleotide-gated (CNG) nonselective cation channel involved in sensory transduction (pqac-00000006, pqac-00000025, pqac-00000031) |
| Channel subunit type | **α subunit** of the TAX-2/TAX-4 CNG channel; TAX-4 can also form functional homomeric channels (pqac-00000002, pqac-00000028, pqac-00000040) |
| Partner subunit | **TAX-2** (β subunit), which enhances TAX-4 channel activity in heteromeric channels (pqac-00000002, pqac-00000028, pqac-00000040) |
| Neurons expressing TAX-4 | Strong evidence supports expression/requirement in multiple head sensory neurons including **ASE, AWC, AWB, AFD, ASI, ASJ, ASG, ASK**; later pathway summaries also place TAX-4 in **BAG** and **PQR** sensory signaling contexts (pqac-00000012, pqac-00000025, pqac-00000031, pqac-00000041) |
| Subcellular localization | Localized to **sensory cilia / ciliary membrane**; in AFD, TAX-4 colocalizes with thermosensory guanylyl cyclases at sensory endings (pqac-00000008, pqac-00000009, pqac-00000022) |
| Gating ligand | Activated preferentially by **cGMP**; channel has higher affinity for cGMP than cAMP, though cyclic nucleotides gate the channel through the CNBD (pqac-00000006, pqac-00000017, pqac-00000040) |
| Ion selectivity | **Nonselective cation channel** permeable to monovalent cations and reported as permeable to **Na+** and **Ca2+** in sensory signaling; extracellular Ca2+/Mg2+ can block permeation in structural/biophysical analyses (pqac-00000015, pqac-00000016, pqac-00000031) |
| Key domains / architecture | Canonical CNG architecture with **S1-S6 transmembrane domain**, **pore loop/selectivity filter**, **C-linker/gating ring**, and **cyclic nucleotide-binding domain (CNBD)**; selectivity filter includes **T376-I377-G378-E379** (pqac-00000014, pqac-00000015, pqac-00000018) |
| Structural resolution | Cryo-EM structure solved at **3.5 Å** in the cGMP-bound open state (pqac-00000017, pqac-00000018, pqac-00000019) |
| Mutant phenotypes | Loss of tax-4 causes major **chemotaxis** and **thermotaxis** defects, altered food-state sensory gene expression, enhanced **cold tolerance** in specific contexts, ectopic neurite initiation in ASJ, and **lifespan extension** with intestinal UPRER activation; one study reported mean lifespan increase from **19.02 to 29.95 days** in tax-4(p678) mutants, while pharmacologic CNG inhibition extended lifespan by ~**18%** (31 to 38 days) (pqac-00000011, pqac-00000032, pqac-00000033, pqac-00000034, pqac-00000035, pqac-00000039) |
| Key signaling pathways | Core component of **cGMP-dependent sensory transduction**. In **AWC**: GPCRs → **ODR-3** → **ODR-1/DAF-11** guanylyl cyclases or PDE regulation → cGMP → TAX-4/TAX-2 opening. In **AFD**: **GCY-8/GCY-18/GCY-23** receptor guanylyl cyclases act upstream of TAX-4/TAX-2 to drive thermosensation and adaptation (pqac-00000021, pqac-00000023, pqac-00000027, pqac-00000028, pqac-00000040) |


*Table: This table summarizes the core molecular, cellular, structural, and functional properties of the C. elegans TAX-4 cyclic nucleotide-gated channel. It is useful as a compact reference linking TAX-4 identity, localization, signaling pathways, and experimentally observed mutant phenotypes.*