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. Author manuscript; available in PMC: 2009 Jun 8.
Published in final edited form as: J Biol Chem. 2002 Jun 7;277(41):38700–38708. doi: 10.1074/jbc.M202348200

Fig. 9. NGF-induced modification of kinetic parameters of TrkA trafficking.

Fig. 9

A, schematic representation of the different TrkA locations in PC12 cells. Half-lives (min) of receptor movements between compartments are indicated (values in red and black are with and without NGF, respectively). B, the cell surface level of TrkA receptor is the result of an equilibrium between movements of the receptor to and from the cell surface. Equilibrium constant values are different in the absence or presence of NGF. Upon the modification of kinetic constants by NGF, there is a two-phase transition (T1 and T2) to reach a new equilibrium. The T1 transition step corresponds to the establishment of a new equilibrium at the cell surface. During this phase, the bulk of the TrkA receptor located at the cell surface before growth factor treatment is internalized. The T2 phase corresponds to lysosomal targeting of this initial wave of internalized receptor. The differences between the E1 (Eq1) and E2 (Eq2) states depend on the decrease in the overall quantity of cellular receptor and the inversion of the ratio of cell surface to the internalized receptor (2 :0.7).