Fibrillin-1 Inhibits Early Adipogenic Commitment Via αvβ3 Integrin Signaling

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Biology

Background:

• Fibrillin-1 is crucial for connective tissues and its mutations cause Marfan syndrome.
• Fibrillin-1 deficiency is linked to obesity, particularly in older individuals, by affecting adipogenic stem cell differentiation.
• The specific cell receptors and signaling pathways involved in fibrillin-1's regulation of adipogenesis were previously unknown.

Purpose of the Study:

• To elucidate the molecular mechanisms by which fibrillin-1 influences adipogenic differentiation.
• To identify the cell surface receptors and downstream signaling cascades involved in fibrillin-1's anti-adipogenic effects.
• To investigate the role of integrin binding motifs in fibrillin-1's function during early adipogenesis.

Main Methods:

• Used recombinant fibrillin-1 fragments with active (RGD) or inactive (RGA) integrin-binding motifs.
• Tested the effects of these fragments on adipogenic differentiation in primary mesenchymal progenitors and 3T3-L1 cells.
• Employed siRNA gene silencing and pharmacological inhibitors to investigate the roles of integrin αvβ3, Fak, Src, and Erk signaling pathways.

Main Results:

• Recombinant fibrillin-1 with an active RGD motif inhibited early adipogenic differentiation, while the RGA control had no effect.
• Inhibition of adipogenesis by fibrillin-1 required integrin αvβ3 and triggered the Fak-Src-Erk signaling cascade.
• This cascade suppressed key adipogenic transcription factors (Cebpα and Pparγ), maintaining progenitor cell undifferentiation.
• Inhibiting Fak, Src, or Erk rescued the anti-adipogenic effect of fibrillin-1.

Conclusions:

• Fibrillin-1 negatively regulates early adipogenic differentiation through engagement of integrin αvβ3.
• The integrin αvβ3-Fak-Src-Erk signaling axis acts as a critical checkpoint, limiting excessive adipogenesis.
• This pathway provides a novel molecular explanation for fibrillin-1's role in adiposity regulation and Marfan syndrome phenotypes.