Defective SLC6A5 causes hyperekplexia 3 (HKPX3)

The amino acid glycine (Gly) plays an important role in neurotransmission. Its action is terminated by rapid re-uptake into the pre-synaptic terminal or surrounding glial cells. This re-uptake is mediated by the sodium- and chloride-dependent glycine transporters 1 and 2 (GLYT1 and GLYT2 respectively). GLYT2 is encoded by the human gene SLC6A5 and is predominantly expressed in the medulla. Defects in SLC6A5 cause startle disease (STHE or hyperekplexia (HKPX3; MIM:614618)), a neurologic disorder characterised by neonatal hypertonia, an exaggerated startle response to tactile or acoustic stimuli, and life-threatening neonatal apnea. Sometimes symptoms resolve in the first year of life.

Summary from Reactome (R-HSA-5619089), read 2026-09-23.