TFG-1 function in protein secretion and oncogenesis

Abstract

Export of proteins from the endoplasmic reticulum (ER) in COPII-coated vesicles occurs at defined sites, which contain the scaffolding protein Sec16. We identify TFG-1, a new conserved regulator of protein secretion that interacts directly with SEC-16 and controls the export of cargoes from the ER in C. elegans. Hydrodynamic studies indicate that TFG-1 forms hexamers, which facilitate the co-assembly of Sec16 with COPII subunits. Consistent with these findings, TFG-1 depletion leads to a dramatic decline in both SEC-16 and COPII levels at ER exit sites. The amino-terminus of human TFG was identified previously as a fusion partner of two protein kinases, creating a pair of oncogenes. We propose that fusion of these kinases to TFG relocalizes their activities to ER exit sites, where they prematurely phosphorylate substrates during ER export. Our findings provide a mechanism by which translocations involving TFG can result in cellular transformation and oncogenesis.

Regulation of ubiquitin-dependent cargo sorting by multiple endocytic adaptors at the plasma membrane

“…Hydrodynamic studies and immunoblotting of extracts and immunoprecipitates were performed as described (42). To determine whether endogenous ESCRT-0 could interact with various fragments of recombinant EHS-1, ITSN-1, or FCHO-1, extracts were generated from embryos that were subsequently subjected to sonication in lysis buffer.…”

“…The generation of animals expressing fluorescent fusions with CAV-1, MVB-12, and clathrin light chain were described (26,42). Double-stranded RNA (dsRNA) was synthesized as described (42) from templates prepared by using specific primers to amplify N2 genomic DNA. For RNAi experiments, early L4 stage hermaphrodites were soaked in dsRNA for 24 h at 20°C within a humidified chamber.…”

“…Adult hermaphrodites were grown synchronously in liquid culture, and embryonic lysates were generated for immunoprecipitations as described (42). For mass spectrometry, proteins were precipitated by using TCA and were subsequently processed for MudPIT analysis (42).…”

“…Acquisition parameters and image analysis (including linescan analysis and the creation of kymographs) was performed by using Nikon Elements (confocal) or Metamorph (TIRF) software. Immunofluorescence of fixed embryos was performed as described (42) by using directly labeled rabbit antibodies at a concentration of 1 μg/mL 30-40 Z sections at 0.2-mm steps were acquired (depending on sample thickness). To calculate the fluorescence intensity of specific proteins, the total intensity in a box containing the signal (from a maximum intensity projection) was measured and the camera background was subtracted.…”

Novel Approaches in Anaplastic Thyroid Cancer Therapy

“…Analogous to chromosomal rearrangements involving RET, several TFG fusion proteins have been shown to result in the hyperactivation of MAPK kinase signaling [52][53][54][55]. Endogenous TFG localizes to specialized subdomains of the endoplasmic reticulum that are responsible for the biogenesis of vesicles that carry secretory cargoes out of cells [55].…”