CD44 acts through RhoA to regulate YAP signaling.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The Hippo pathway is crucial for cellular processes and pathogenesis.
• Yeast homolog of Apaf-1 (YAP) is a key downstream effector of the Hippo pathway, regulated by Lats1/2 kinases.
• Upstream regulators of the Hippo pathway remain incompletely understood.

Purpose of the Study:

• To investigate the role of CD44 in regulating the Hippo-YAP pathway.
• To elucidate the signaling mechanisms by which CD44 influences YAP.
• To determine the functional consequences of CD44-mediated YAP regulation.

Main Methods:

• RNA interference (RNAi) to knockdown CD44 and YAP.
• Western blotting to assess protein expression (YAP, Mst1, Lats1, RhoA, CTGF, Cyr61, EDN1).
• Quantitative real-time PCR (qRT-PCR) for mRNA expression analysis.
• Cellular assays for apoptosis, proliferation, cell cycle, and migration.
• Overexpression of constitutively active RhoA (RhoA-V14).

Main Results:

• CD44 knockdown reduced YAP expression and nuclear localization without affecting upstream kinases Mst1 and Lats1.
• Downregulation of CD44 decreased mRNA levels of YAP downstream targets (CTGF, Cyr61, EDN1).
• CD44 knockdown inhibited RhoA expression, and RhoA knockdown mimicked YAP downregulation.
• Overexpression of RhoA-V14 rescued YAP expression decrease caused by CD44 knockdown.
• CD44 downregulation promoted apoptosis and inhibited proliferation, cell cycle, and migration, mirroring YAP knockdown effects.

Conclusions:

• CD44 regulates YAP expression and localization through RhoA signaling.
• The Hippo-YAP pathway is modulated by CD44 via the RhoA signaling axis.
• These findings provide novel insights into the upstream regulatory mechanisms of the Hippo-YAP pathway.