Functional maturation of cytochromes P450 3A4 and 2D6 relies on GAPDH- and Hsp90-Dependent heme allocation

Discovery and binding mode of small molecule inhibitors of the apo form of human TDO2

“…Our work has several limitations which need to be addressed with further experiments. The kinetics of heme association with (or active insertion into) TDO2 and its dissociation rate in living cells needs to be further explored, in a similar way to the recent studies on cytochrome P450 enzyme maturation [26]. The balance of apo-vs. holo-TDO in different cells and disease states also requires further investigation.…”

Heme allocation in eukaryotic cells relies on mitochondrial heme export through FLVCR1b to cytosolic GAPDH

“…Because heme is chemically reactive and has promiscuous binding properties, its synthesis is tightly controlled and its intracellular transport has long been imagined to involve macromolecular carriers 2 , 4 , 5 . Of all the proteins or other macromolecules that have been proposed, the protein glyceraldehyde phosphate dehydrogenase (GAPDH), an enzyme in the glycolytic pathway that is ubiquitously expressed and known to perform alternative moonlighting functions 6 – 8 , has recently emerged as a premier intracellular heme chaperone 9 , based on findings that GAPDH binding of mitochondrially-generated heme is required for and coupled to intracellular heme delivery to numerous targets including hemoglobins α, β, and γ 10 , myoglobin 10 , nitric oxide synthases 11 – 13 soluble guanylyl cyclase β-subunit (sGCβ) 14 , cytochromes P450 15 , heme oxygenase 2 16 , indoleamine dioxygenase 1 (IDO1) and tryptophan dioxygenase (TDO) 17 . Insertion of the GAPDH-sourced heme into recipient target proteins is the final downstream step in heme delivery, and is now understood to require the cell chaperone protein Hsp90, which is typically bound to the heme-free (apo-) forms of the recipient proteins and drives their heme insertions in an ATP-driven process 18 .…”

Heme allocation in eukaryotic cells relies on mitochondrial heme export through FLVCR1b to cytosolic GAPDH

“…Because heme is chemically reactive and has promiscuous binding properties, its synthesis is tightly controlled and its intracellular transport has long been imagined to involve macromolecular carriers 2,4,5 . Of all the proteins or other macromolecules that have been proposed, the protein glyceraldehyde phosphate dehydrogenase (GAPDH), an enzyme in the glycolytic pathway that is ubiquitously expressed and known to perform alternative moonlighting functions [6][7][8] , has recently emerged as a premier intracellular heme chaperone 9 , based on findings that GAPDH binding of mitochondrially-generated heme is required for and coupled to intracellular heme delivery to numerous targets including hemoglobins α, β, and γ 10 , myoglobin 10 , nitric oxide synthases [11][12][13] soluble guanylyl cyclase β-subunit (sGCβ) 14 , cytochromes P450 15 , heme oxygenase 2 16 , indoleamine dioxygenase 1 (IDO1) and tryptophan dioxygenase (TDO) 17 . Insertion of the GAPDH-sourced heme into recipient target proteins is the final downstream step in heme delivery, and is now understood to require the cell chaperone protein Hsp90, which is typically bound to the heme-free (apo-) forms of the recipient proteins and drives their heme insertions in an ATP-driven process 18 .…”