GCK and Hypoglycemia: GKRP expression is a plausible indicator of brain cell metabolic sensitivity, as GKRP-expressing hindbrain A2 noradrenergic neurons exhibit neurotransmitter biosynthetic enzyme, GCK, and KATP channel sulfonylurea receptor-1 subunit transcriptional reactivity to hypoglycemia, yet these gene profiles are hypoglycemia-insensitive in A2 nerve cells lacking GKRP protein [28].