Functions and Regulation of Circular Dorsal Ruffles

The regulation of macropinocytosis, a specialised endocytosis pathway, is important for immune cell function. However, it is not known whether the biogenesis of macropinosomes involves one or more distinct pathways. We previously identified sorting nexin 5 (SNX5) as a regulator of macropinocytosis in macrophages. Here, we show that bone-marrow-derived macrophages from SNX5-knockout mice had a 60-70% reduction in macropinocytic uptake of dextran or ovalbumin, whereas phagocytosis and retrograde transport from the plasma membrane to the Golgi was unaffected. In contrast, deficiency of SNX5 had no effect on macropinocytosis or antigen presentation by dendritic cells. Activation of macrophages with CSF-1 resulted in a localisation of SNX5 to actin-rich ruffles in a manner dependent on receptor tyrosine kinases. SNX5-deficient macrophages showed a dramatic reduction in ruffling on the dorsal surface following CSF-1 receptor activation, whereas peripheral ruffling and cell migration were unaffected. We demonstrate that SNX5 is acting upstream of actin polymerisation following CSF-1 receptor activation. Overall, our findings reveal the important contribution of dorsal ruffing to receptoractivated macropinocytosis in primary macrophages and show that SNX5 selectively regulates macropinosomes derived from the dorsal ruffles.

Section: Discussioncontrasting

confidence: 42%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sorting nexin 5 (SNX5) selectively regulates dorsal ruffle-mediated macropinocytosis in primary macrophages

Lim

Gosavi

Mintern

et al. 2015

“…3) rapidly redistribute to CDRs upon PDGF stimulation and that this redistribution is linked to focal adhesion turnover and cell migration (Gu et al, 2011;Hoon et al, 2012). We first addressed whether MICAL-L1 KD in human fibroblasts affected focal adhesions at steady state.…”

Section: Mical-l1 Is Required For Pdgf-induced Focal Adhesion Turnovermentioning

confidence: 99%

Regulation of Src trafficking and activation by the endocytic regulatory proteins MICAL-L1 and EHD1

Reinecke

Katafiasz

Naslavsky

et al. 2014

Localization of the non-receptor tyrosine kinase Src to the cell periphery is required for its activation and to mediate focal adhesion turnover, cell spreading and migration. Inactive Src localizes to a perinuclear compartment and the movement of Src to the plasma membrane is mediated by endocytic transport. However, the precise pathways and regulatory proteins that are responsible for SRC transport are incompletely understood. Here, we demonstrate that Src partially colocalizes with the endocytic regulatory protein MICAL-L1 (molecule interacting with CasL-like protein 1) in mammalian cells. Furthermore, MICAL-L1 is required for growthfactor-and integrin-induced Src activation and transport to the cell periphery in HeLa cells and human fibroblasts. Accordingly, MICAL-L1 depletion impairs focal adhesion turnover, cell spreading and cell migration. Interestingly, we find that the MICAL-L1 interaction partner EHD1 (EH domain-containing protein 1) is also required for Src activation and transport. Moreover, the MICAL-L1-mediated recruitment of EHD1 to Src-containing recycling endosomes is required for the release of Src from the perinuclear endocytic recycling compartment in response to growth factor stimulation. Our study sheds new light on the mechanism by which Src is transported to the plasma membrane and activated, and provides a new function for MICAL-L1 and EHD1 in the regulation of intracellular non-receptor tyrosine kinases.

“…During this process, extracellular growth factors activate receptor tyrosine kinase (RTK)-dependent signaling, leading to extensive actin cytoskeleton remodeling and to the formation of unique specialized structures, such as circular dorsal ruffles (CDRs), lamellipodia and filopodia. CDRs are highly dynamic ring-shaped structures that are rich in filamentous actin (F-actin), and form on the dorsal surface of epithelial cells and fibroblasts in response to stimulation with growth factors, such as platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) (Hoon et al, 2012). Moreover, CDRs have been implicated in macropinocytosis (Dowrick et al, 1993), recycling of integrins (Gu et al, 2011), rapid actin cytoskeleton remodeling during cell migration (Buccione et al, 2004), and in the internalization and sequestration of a number of RTKs, leading to their downregulation (Orth and McNiven, 2006).…”

Section: Introductionmentioning

confidence: 99%

Arl13b and the non-muscle myosin heavy chain IIA are required for circular dorsal ruffle formation and cell migration

Casalou

Seixas

Portelinha

et al. 2014

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 ring-shaped 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.