Ion-gated ion channels Today I've heard for the first time of calcium-gated ion channels but find it hard to get an idea how they work, where they are located, and which role they play. I assume calcium-gated ion channels are just a special form of ion-gated ion channels, which would be a fourth group of ion channels next to voltage-, lipid-, and ligand-gated ion channels (with ligands being some larger molecules). But on ion-gated ion channels even less is to be found on the internet. One specific paper that mentions ion-gated ion channels is this (Experimental Neurology, 2001) One paper that mentions calcium-gated ion channels is this (New England Journal of Medicine, 2015) Where do I find a general introduction into ion-gated ion channels - if they exist?

The main families of calcium-gated channels I am aware of are the calcium-gated potassium channels and the internal ryanodine receptors involved in calcium-induced calcium release - you could start from those linked Wikipedia articles.

I wouldn't really make these a fourth category, they should either be thought of as voltage-gated channels that are modulated by intracellular calcium, or as ligand-gated channels - the ligand just happens to be a calcium ion.

Some channels in this category are not influenced by calcium directly but via calmodulin, which is a common mediator of calcium-driven intracellular influences.