ErbB1 dimerization is promoted by domain co-confinement and stabilized by ligand binding.
The extent to which ligand occupancy and dimerization contribute to erbB1 signaling is controversial. To examine this, we used two-color quantum-dot tracking for visualization of the homodimerization of human erbB1 and quantification of the dimer off-rate (k(off)) on living cells. Kinetic parameters were extracted using a three-state hidden Markov model to identify transition rates between free, co-confined and dimerized states. We report that dimers composed of two ligand-bound receptors are long-lived and their k(off) is independent of kinase activity. By comparison, unliganded dimers have a more than four times faster k(off). Transient co-confinement of receptors promotes repeated encounters and enhances dimer formation. Mobility decreases more than six times when ligand-bound receptors dimerize. Blockade of erbB1 kinase activity or disruption of actin networks results in faster diffusion of receptor dimers. These results implicate both signal propagation and the cortical cytoskeleton in reduced mobility of signaling-competent erbB1 dimers.
Department of Pathology, University of New Mexico School of Medicine, Albuquerque, New Mexico, USA.
Shalini T
ST
Low-Nam
Keith A
KA
Lidke
Patrick J
PJ
Cutler
Rob C
RC
Roovers
Paul M P
PM
van Bergen en Henegouwen
Bridget S
BS
Wilson
Diane S
DS
Lidke
D045744:Cell Line, Tumor; D019281:Dimerization; D066246:ErbB Receptors / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008024:Ligands; D011485:Protein Binding; D011487:Protein Conformation
D008024:Ligands; D066246:ErbB Receptors