Proteome of Acidic Phospholipid-binding Proteins

Tsujita, Kazuya; Itoh, Toshiki; Kondo, Akihiro; Oyama, Masaaki; Kozuka‐Hata, Hiroko; Irino, Yasuhiro; Hasegawa, Junya; Takenawa, Tadaomi

doi:10.1074/jbc.m109.057018

Cited by 36 publications

(28 citation statements)

References 35 publications

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“…We observed the same Arf1-dependent phenomenon when testing binding of Sec7 f to liposomes prepared from Folch lipids (which BIG1 and BIG2 were found to bind in a proteomic study (Tsujita et al, 2010)), or when the phosphoinositide PI(4)P was omitted from the synthetic TGN-like lipid mix (Figure S2A). This suggests the presence of activated Arf1 may be more important than lipid composition for stable association of Sec7 with membranes.…”

Section: Resultssupporting

confidence: 53%

The Sec7 Arf-GEF Is Recruited to the trans-Golgi Network by Positive Feedback

2012

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Summary Arf GTPases are key regulators of both retrograde and anterograde traffic at the Golgi complex. The Golgi-localized Arf activators, Arf-GEFs (guanine exchange factor) of the BIG/GBF family, are poorly understood in terms of both their regulatory and localization mechanisms. We have performed a detailed kinetic characterization of a functional Golgi Arf-GEF, the trans-Golgi network (TGN)-localized Sec7 protein from yeast. We demonstrate that Sec7 is regulated by both autoinhibition and positive feedback. We show that positive feedback arises through the stable recruitment of Sec7 to membranes via its HDS1 domain by interaction with its product, activated Arf1. This interaction mediates localization of Sec7 to the TGN, as deletion of the HDS1 domain or mutation of the HDS1 domain in combination with deletion of Arf1 significantly increases cytoplasmic localization of Sec7. Our results lead us to propose a model in which Arf-GEF recruitment is linked to Golgi maturation via Arf1 activation.

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Section: Resultssupporting

confidence: 53%

The Sec7 Arf-GEF Is Recruited to the trans-Golgi Network by Positive Feedback

2012

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“…A single conserved residue in this patch, Arg30, can be mutated to Asp (R30D) and high affinity F-actin binding is lost. This observation has been confirmed by mutating the equivalent residue in Coro1A and Coro1C 13, 14 . Interestingly, this residue is not conserved in Type II coronins, suggesting that these proteins may have an alternate actin binding surface with different characteristics 11 .…”

Section: The Mechanism Of Type I Coronin Functionmentioning

confidence: 56%

Unraveling the enigma: progress towards understanding the coronin family of actin regulators

Chan¹,

Creed²,

Bear

2011

Trends in Cell Biology

150

139

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Coronins are a conserved family of actin cytoskeleton regulators that promote cell motility and modulate other actin-dependent processes. Although these proteins have been known for twenty years, substantial progress has been made in the last five years towards understanding coronins. Here, we review this progress, place it into the context of what was already known and pose several questions that remain to be addressed. In particular, we cover the emerging consensus about the role of Type I coronins in coordinating the function of Arp2/3 complex and ADF/cofilin proteins. This coordination plays an important role in leading edge actin dynamics and overall cell motility. Finally, we discuss the roles played by the more exotic coronins of the Type II and III classes in cellular processes away from the leading edge.

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“…Actin dynamics is regulated by actin-binding proteins, which are temporally and spatially regulated by PIP 2 . We focused our analysis on Coronin 1A because Coronin 1A is reported to bind both PIP 2 and actin filaments (17) and is involved in phagocytosis in HL-60 cells (16). We first determined the expression level of Coronin 1A in parental and Rab27a knockdown HL-60 cells by immunoblot analysis (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…of Biochemistry, Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, Himeji 670-8524, Japan. is believed to be a key regulator of actin disassembly whose activity is regulated by PIP 2 (17). In this study, we investigated whether Rab27a is directly involved in the process of phagocytosis in the complementmediated pathway.…”

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confidence: 99%

Rab27a Negatively Regulates Phagocytosis by Prolongation of the Actin-coating Stage around Phagosomes

Yokoyama

Kaji²,

et al. 2011

Journal of Biological Chemistry

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Rab27a, a Rab family small GTPase, is involved in the exocytosis of secretory granules in melanocytes and cytotoxic Tcells. Rab27a mutations cause type 2 Griscelli syndrome, which is characterized by immunodeficiency, including uncontrolled macrophage activation known as hemophagocytic syndrome. However, the role of Rab27a in phagocytosis remains elusive. Here, using macrophage-like differentiated HL-60 cells and C3bi-opsonized zymosan as a pathogen-phagocyte model, we show that Rab27a negatively regulates complementmediated phagocytic activity in association with F-actin remodeling. We found that transfection of Rab27a shRNA into HL-60 cells enhances complement-mediated phagocytosis. To clarify the mechanisms underlying the elevated phagocytosis in Rab27a knockdown cells, we analyzed the process of phagosome formation focusing on F-actin dynamics: F-actin assembly, followed by F-actin extension around the particles and the subsequent degradation of F-actin, leading to internalization of the particles enclosed in phagosomes. Microscopic analysis revealed that these actin-related processes, including F-actin coating and F-actin degradation, proceed more rapidly in Rab27a knockdown cells than in control HL-60 cells. Both elevated phagocytosis and accelerated F-actin remodeling were restored by expression of rescue-Rab27a and Rab27a-Q78L (GTP-bound form), but not by Rab27a-T23N (GDP-bound form). Furthermore, an increased accumulation of Coronin 1A surrounding F-actin coats was observed in Rab27a knockdown cells, suggesting that the function of Coronin 1A is related to the regulation of the F-actin coating. Our findings demonstrate that Rab27a plays a direct regulatory role in the nascent process of phagocytosis by prolongation of the stage of actin coating via suppression of Coronin 1A. This study may contribute to an explanation of the underlying mechanisms of excessive phagocytosis observed in Griscelli syndrome.

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Proteome of Acidic Phospholipid-binding Proteins

Cited by 36 publications

References 35 publications

The Sec7 Arf-GEF Is Recruited to the trans-Golgi Network by Positive Feedback

The Sec7 Arf-GEF Is Recruited to the trans-Golgi Network by Positive Feedback

Unraveling the enigma: progress towards understanding the coronin family of actin regulators

Rab27a Negatively Regulates Phagocytosis by Prolongation of the Actin-coating Stage around Phagosomes

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