Altered TGF-beta endocytic trafficking contributes to the increased signaling in Marfan syndrome

作者：Siegert Anna Maria; Serra Peinado Carla; Gutierrez Martinez Enric; Rodriguez Pascual Fernando; Fabregat Isabel; Egea Gustavo

来源：Biochimica et Biophysica Acta-Molecular Basis of Disease, 2018, 1864(2): 554-562.

DOI：10.1016/j.bbadis.2017.11.015

• Marfan syndrome
• Human vascular smooth muscle cells
• Membrane trafficking
• TGF-beta signaling
• Endocytosis

The main cardiovascular alteration in Marfan syndrome (MFS) is the formation of aortic aneurysms in which augmented TGF-beta signaling is reported. However, the primary role of TGF-beta signaling as a molecular link between the genetic mutation of fibrillin-1 and disease onset is controversial. The compartmentalization of TGF-beta endocytic trafficking has been shown to determine a signaling response in which clathrin-dependent internalization leads to TGF-beta signal propagation, and caveolin-1 (CAV-1) associated intemalization leads to signal abrogation. We here studied the contribution of endocytic trafficking compartmentalization to increased TGF-beta signaling in vascular smooth muscle cells (VSMC) from MFS patients. We examined molecular components involved in clathrin-(SARA, SMAD2) and caveolin-1-(SMAD7, SMURF2) dependent endocytosis. Marfan VSMC showed higher recruitment of SARA and SMAD2 to membranes and their increased interaction with TGF-beta receptor II, as well as higher colocalization of SARA with the early endosome marker EEA1. We assessed TGF-beta internalization using a biotinylated ligand (b-TGF-beta), which colocalized equally with either EEA1 or CAVA in VSMC from Marfan patients and controls. However, in Marfan cells, colocalization of b-TGF-beta with SARA and EEA1 was increased and accompanied by decreased colocalization with CAV-1 at EEA1-positive endosomes. Moreover, Marfan VSMC showed higher transcriptional levels and membrane enrichment of RAB5. Our results indicate that increased RAB5-associated SARA localization to early endosomes facilitates its TGF-beta receptor binding and phosphorylation of signaling mediator SMAD2 in Marfan VSMC. This is accompanied by a reduction of TGF-beta sorting into multifunctional vesicles containing cargo from both internalization pathways.

• 出版日期2018-2