Self assembly of the transmembrane domain promotes signal transduction through the erythropoietin receptor.
Hematopoietic cytokine receptors, such as the erythropoietin receptor (EpoR), are single membrane-spanning proteins. Signal transduction through EpoR is crucial for the formation of mature erythrocytes. Structural evidence shows that in the unliganded form EpoR exists as a preformed homodimer in an open scissor-like conformation precluding the activation of signaling. In contrast to the extracellular domain of the growth hormone receptor (GHR), the structure of the agonist-bound EpoR extracellular region shows only minimal contacts between the membrane-proximal regions. This evidence suggests that the domains facilitating receptor dimerization may differ between cytokine receptors. We show that the EpoR transmembrane domain (TM) has a strong potential to self interact in a bacterial reporter system. Abolishing self assembly of the EpoR TM by a double point mutation (Leu 240-Leu 241 mutated to Gly-Pro) impairs signal transduction by EpoR in hematopoietic cells and the formation of erythroid colonies upon reconstitution in erythroid progenitor cells from EpoR(-/-) mice. Interestingly, inhibiting TM self assembly in the constitutively active mutant EpoR R129C abrogates formation of disulfide-linked receptor homodimers and consequently results in the loss of ligand-independent signal transduction. Thus, efficient signal transduction through EpoR and possibly other preformed receptor oligomers may be determined by the dynamics of TM self assembly.
Max-Planck-Institute of Immunobiology, Freiburg 79108, Germany.
K F
KF
Kubatzky
W
W
Ruan
R
R
Gurezka
J
J
Cohen
R
R
Ketteler
S S
SS
Watowich
D
D
Neumann
D
D
Langosch
U
U
Klingmüller
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids; D011233:Precipitin Tests; D017467:Receptors, Erythropoietin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
D017467:Receptors, Erythropoietin