Controlled Plasma Membrane Delivery of FGFR1 and Modulation of Signaling by a Novel Regulated Anterograde RTK Transport Pathway.

Controlled Plasma Membrane Delivery of FGFR1 and Modulation of Signaling by a Novel Regulated Anterograde RTK Transport Pathway.

Cancers (2023-12-23)

Claire Leist Hinsch, Jagadish Kummetha Venkata, Tien Hsu, Vincent Dammai

ABSTRACT

How human FGFR1 localizes to the PM is unknown. Currently, it is assumed that newly synthesized FGFR1 is continuously delivered to the PM. However, evidence indicates that FGFR1 is mostly sequestered in intracellular post-Golgi vesicles (PGVs) under normal conditions. In this report, live-cell imaging and total internal reflection fluorescence microscopy (TIRFM) were employed to study the dynamics of these FGFR1-positive vesicles. We designed recombinant proteins to target different transport components to and from the FGFR1 vesicles. Mouse embryoid bodies (mEBs) were used as a 3D model system to confirm major findings. Briefly, we found that Rab2a, Rab6a, Rab8a, RalA and caveolins are integral components of FGFR1-positive vesicles, representing a novel compartment. While intracellular sequestration prevented FGFR1 activation, serum starvation and hypoxia stimulated PM localization of FGFR1. Under these conditions, FGFR1 C-terminus acts as a scaffold to assemble proteins to (i) inactivate Rab2a and release sequestration, and (ii) assemble Rab6a for localized activation of Rab8a and RalA-exocyst to deliver the receptor to the PM. This novel pathway is named Regulated Anterograde RTK Transport (RART). This is the first instance of RTK regulated through control of PM delivery.

MATERIALS

Product Number

Brand

Product Description

124018

Sigma-Aldrich

Akt Inhibitor VIII, Isozyme-Selective, Akti-1/2, Akt Inhibitor VIII, Isozyme-Selective, Akti-1/2, CAS 612847-09-3, is a cell-permeable, reversible inhibitor of Akt1/Akt2 (IC₅₀ = 58 nM, 210 nM, & 2.12 µM for Akt1, Akt2, and Akt3, respectively).

662005

Sigma-Aldrich

U0126, U0126, CAS 109511-58-2, is a potent and specific inhibitor of MEK1 (IC₅₀ = 72 nM) and MEK2 (IC₅₀ = 58 nM). The inhibition is noncompetitive with respect to both ATP and ERK.

572630

Sigma-Aldrich

SU5402, SU5402, CAS 215543-92-3, is a cell-permeable, reversible, and ATP-competitive inhibitor of the tyrosine kinase activity of FGFR1 (IC₅₀ = 10-20 µM in the presence of 1 mM ATP).