The Arf-like protein Arl13b has been implicated in ciliogenesis and Sonic hedgehog signaling. Furthermore, we have previously shown that it regulates endocytic recycling traffic and interacts with actin. Herein, we report that the non-muscle myosin heavy chain IIA, also known as Myh9, is an Arl13b effector. Moreover, we found that both proteins localized to circular dorsal ruffles (CDRs) induced by platelet-derived growth factor stimulation and are required for their formation. CDRs are

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... ped actin-dependent structures formed on the dorsal cell surface and are involved in diverse processes, such as macropinocytosis, integrin recycling, internalization of receptor tyrosine kinases and cell migration. We found that Arl13b or Myh9 silencing impaired cell migration, suggesting that Arl13b is required for this function through the interaction with Myh9. Moreover, Arl13b silencing impaired neural crest cell migration in zebrafish embryos. Furthermore, we showed that Arl13b is required for the formation of CDRs in migrating cells. Thus, our results indicate a new role for Arl13b in actin cytoskeleton remodeling through the interaction with Myh9, by driving the formation of CDRs necessary for cell migration. Immunofluorescence Cells grown on glass coverslips were serum-starved for 5 to 16 hours, stimulated or not with PDGF (30 ng/ml) for different times, washed with PBS and fixed in 4% paraformaldehyde in PBS for 15-20 minutes at room temperature. After quenching with 50 mM NH 4 Cl in PBS and blocking and permeabilizing with PBS, 0.5% BSA and 0.1% saponin for 10 minutes at room temperature, anti-Myh9, anti-cortactin, anti-EEA1 antibodies or Alexa-Fluor-568-conjugated phalloidin (0.2 to 0.8 U/ml)