Multiple routes of endocytic internalization of PDGFRβ contribute to PDGF-induced STAT3 signaling

Abstract

Platelet-derived growth factor receptor β (PDGFRβ) is a receptor tyrosine kinase which upon activation by PDGF-BB stimulates cell proliferation, migration and angiogenesis. Ligand binding induces intracellular signaling cascades but also internalization of the receptor, eventually resulting in its lysosomal degradation. However, endocytic trafficking of receptors often modulates their downstream signaling. We previously reported that internalization of PDGFRβ occurs via dynamin-dependent and -independent pathways but their further molecular determinants remained unknown. Here we show that, in human fibroblasts expressing endogenous PDGFRβ and stimulated with 50 ng/ml PDGF-BB, ligand-receptor uptake proceeds via the parallel routes of clathrin-mediated endocytosis (CME) and clathrin-independent endocytosis (CIE). CME involves the canonical AP2 complex as a clathrin adaptor, while CIE requires RhoA-ROCK, Cdc42 and galectin-3, the latter indicating lectinmediated internalization via clathrin-independent carriers (CLICs). Although different uptake routes appear to be partly interdependent, they cannot fully substitute for each other. Strikingly, inhibition of any internalization mechanism impaired activation of STAT3 but not of other downstream effectors of PDGFRβ. Our data indicate that multiple routes of internalization of PDGFRβ contribute to a transcriptional and mitogenic response of cells to PDGF.

Regulator of G‐protein signaling 5 regulates the shift from perivascular to parenchymal pericytes in the chronic phase after stroke

“…Another possible explanation for the reduced protein levels of PDGFR-β in WT mice could be that activation of the PDGFR-β pathway led to internalization of PDGFR-β and thereby reduction in the total PDGFR-β protein. We and others have previously shown that stimulation of PDGFR-β results in decreased surface expression and internalization, which are associated with increased phosphorylation of the receptor (30–34). The increased activation of PDGFR-β as indicated by the increased ratio of pPDGFR-β to total PDGFR-β in WT mice might facilitate pericyte detachment from the vessels and increase the density of parenchymal pericytes.…”

FGFR1 clustering with engineered tetravalent antibody improves the efficiency and modifies the mechanism of receptor internalization

“…Protein A Sepharose and Glutathione Sepharose resins were from GE Healthcare (Piscataway, NJ, USA). siRNA was from Thermo Fisher Scientific or from GE Dharmacon (Lafayette, CO, USA) as described previously [47].…”

“…Cells were transfected with siRNA against endocytic proteins with Lipofectamine RNAiMAX (Thermo Fisher Scientific), as described previously [47]. U2OS‐R1 cells were treated for 3 days in 5% CO 2 atmosphere at 37 °C with 20 n m Ambion Silencer Select siRNA against clathrin heavy chain (CHC_1 ‐ #s475, CHC_2‐ #s477), a μ2 subunit of the AP2 complex (AP2μ2) (AP2M1_1 ‐ #s3112, AP2M1_2 ‐ #s3113), dynamin‐2 (DNM2_1 ‐ #s4212, DNM2_2 ‐ #s4213), galectin‐3 (GAL3_1 ‐ #s8148, GAL3_2‐ #s8149), CD44 (CD44_1‐ #s2681), ROCK1 (ROCK1_1 ‐ #s12097, ROCK1_2 ‐#s12098), and ROCK2 (ROCK2_1 ‐ #s18161, ROCK2_2‐ #s18162) were from Thermo Fisher Scientific.…”

Melatonin Synergizes with Sorafenib to Suppress Pancreatic Cancer via Melatonin Receptor and PDGFR-β/STAT3 Pathway

“…Notably, PDGFR-β is known to induce STAT3 phosphorylation, and activated STAT3 leads to cell transformation [47,48]. Consequently, elevated STAT3 signaling inhibits apoptosis and supports cancer survival, producing a phenotype similar to chemo-resistance [49].…”