Possible involvement of microfilaments in protein kinase C translocation

Ito, Masahiko; Tanabe, Fuminori; Sato, Akihiko; Ishida, Eiko; Takami, Yoshiyuki; Shigeta, Shirô

doi:10.1016/s0006-291x(89)80151-2

Cited by 26 publications

(11 citation statements)

References 16 publications

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“…Unbound 59 Fe 2 -Tf and bafilomycin were removed by washing the cells in PBS and surface-bound radioactivity was removed by a 120 minutes treatment at 4°C with 10 M 56 Fe 2 -Tf. The cells were next treated with the indicated concentrations of N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7; specific calmodulin inhibitor 32,33 ) for 30 minutes at 4°C. Incorporation of 59 Fe into heme was monitored by incubating the samples at 37°C for the indicated time intervals, washing in PBS, and determining the heme and nonheme radioactivity as mentioned above.…”

Section: Iron Uptake and Incorporation Into Hemementioning

confidence: 99%

Direct interorganellar transfer of iron from endosome to mitochondrion

Sheftel

Zhang

Brown

et al. 2007

Blood

243

180

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Iron is a transition metal whose physicochemical properties make it the focus of vital biologic processes in virtually all living organisms. Among numerous roles, iron is essential for oxygen transport, cellular respiration, and DNA synthesis. Paradoxically, the same characteristics that biochemistry exploits make iron a potentially lethal substance. In the presence of oxygen, ferrous iron (Fe 2؉ ) will catalyze the production of toxic hydroxyl radicals from hydrogen peroxide. In addition, Fe 3؉ is virtually insoluble at physiologic pH. To protect tissues from deleterious effects of Fe, mammalian physiology has evolved specialized mechanisms for extracellular, intercellular, and intracellular iron handling. Here we show that developing erythroid cells, which are taking up vast amounts of Fe, deliver the metal directly from transferrin-containing endosomes to mitochondria (the site of heme biosynthesis), bypassing the oxygen-rich cytosol. Besides describing a new means of intracellular transport, our finding is important for developing therapies for patients with iron loading disorders. IntroductionAlthough its requirement for life in almost all known organisms has been recognized for decades, some of the most fundamental cell biologic processes of iron (Fe) still elude modern science. Mammalian physiology demands a constant source of bioavailible Fe, which is a functional component of hemoproteins, iron-sulfur cluster containing proteins, and other iron proteins. However, in its reduced form (Fe 2ϩ ), iron catalyzes the production of toxic hydroxyl radicals through Fenton chemistry, while the ferric version (Fe 3ϩ ) is virtually insoluble at physiologic pH. [1][2][3] Nevertheless, the adult human body contains approximately 4 g of Fe, more than 80% of which is in hemoglobin (Hb). 4 Under normal conditions, around 2 million red blood cells (RBCs) are produced per second. Hence, erythropoiesis requires approximately 25 mg of iron, daily, all of which is delivered via transferrin (Tf). The plasma contains approximately 3 M diferric Tf, the Fe of which is concentrated in maturing erythroid tissue to the equivalent of 20 mM iron, in the form of Hb. This exceptionally rapid utilization of the potentially toxic metal requires stringent regulation mechanisms that permit efficient production of hemoglobin, while protecting developing red blood cells and other tissues from iron's harmful properties. 5 Virtually every tissue acquires its iron by receptor mediated endocytosis of Tf (for review, see Richardson and Ponka 6 and Hentze et al 7 ): Diferric Tf binds to its cognate receptor on the cell surface; this binding is succeeded by internalization of the receptorligand complex. The release of Fe from Tf is achieved within the endosome by a lowering of the vesicular pH through the activity of the v-ATPase proton pump. After its liberation from Tf in the acidified endosome, Fe must be reduced (possibly by the recently identified Steap3 8 ) before it is transported across the vesicular membrane by the divalent metal transp...

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Section: Iron Uptake and Incorporation Into Hemementioning

confidence: 99%

Direct interorganellar transfer of iron from endosome to mitochondrion

Sheftel

Zhang

Brown

et al. 2007

Blood

243

180

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“…Although this classical model of acute PKC activation (seconds to minutes) stands today as a paradigm for the study of lipid-dependent signal transduction, there is additional biochemical and immunocytochemical evidence to suggest that PKC may translocate to sites other than the plasma membrane (5). Using a variety of PKC agonists, including extracellular agonists and phorbol esters, PKC has been localized to the Golgi complex (6), nuclear envelope (7,8), nucleus (9, 10) mitochondria (11), and/or cytoskeleton (12)(13)(14).…”

Section: Members Of the Protein Kinase C (Pkc)mentioning

confidence: 99%

cPKC-dependent Sequestration of Membrane-recycling Components in a Subset of Recycling Endosomes

Becker

Hannun

2003

Journal of Biological Chemistry

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In addition to the classical role of protein kinase C (PKC) as a mediator of transmembrane signals initiated at the plasma membrane, there is also significant evidence to suggest that a more sustained PKC activity is necessary for a variety of long term cellular responses. To date, the subcellular localization of PKC during sustained activation has not been extensively studied. We report here that long term activation of PKC (1 h) leads to the selective translocation of classical PKC isoenzymes, ␣ and ␤II, to a juxtanuclear compartment. Juxtanuclear translocation of PKC required an intact C1 and C2 domain, and occurred in a microtubule-dependent manner. This juxtanuclear compartment was localized close to the Golgi complex but displayed no overlap with Golgi markers, and was resistant to dispersal with Golgi disrupting agents, brefeldin A and nocodazole. Further characterization revealed that PKC␣ and ␤II translocated to a compartment that colocalized with the small GTPase, rab11, which is a marker for the subset of recycling endosomes concentrated around the microtubule-organizing center/centrosome. Analysis of the functional consequence of cPKC translocation on membrane recycling demonstrated a cPKC-dependent sequestration of transferrin, a marker of membrane recycling, in the cPKC compartment. These results identify a novel site for cPKC translocation and define a novel function for the sustained activation of PKC␣ and ␤II in regulation of recycling components.Members of the protein kinase C (PKC) 1 superfamily of lipiddependent, serine-threonine kinases function as critical signaling intermediates in numerous signal transduction pathways and cellular regulatory processes. Currently, PKC consists of 11 distinct isoenzymes grouped into three subfamilies (classical, novel, and atypical) on the basis of lipid cofactor requirements and structural homology (1). The first PKC kinases to be identified were the calcium-dependent or classical PKC (cPKC) isoenzymes (␣, ␤I, ␤II, and ␥). Members of this subfamily contain a cysteine-rich zinc finger C1 domain, which is the site of sn-1,2-diacylglycerol (DAG) and phorbol ester binding, and a C2 domain which confers calcium-dependent phospholipid binding properties. The novel PKC (nPKC) isoenzymes (␦, ⑀, , ) also contain a C1 domain and bind DAG similar to the classical isoenzymes but display calcium independence due to a truncated, non-functional C2 domain. Lipid regulation of the atypical PKC (aPKC) subfamily ( / , ) is the most divergent due to a truncated, DAG-insensitive C1 domain and no C2 domain (1-3).A key determinant of cellular PKC activation lies in the ability of individual isoenzymes, especially those of cPKC and less so that of nPKC, to translocate to the plasma membrane in response to DAG and tumor-promoting phorbol esters. At the plasma membrane, PKC becomes fully activated and gains access to specific substrates (4). Although this classical model of acute PKC activation (seconds to minutes) stands today as a paradigm for the study of lipid-dependent signal ...

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“…The cytoskeleton has also been involved in the dynamics of PKC movement (Ito et al, 1989;Keenan and Kelleher, 1998). For instance, PKC-␤ binds directly to F-actin (Blobe et al, 1996) and phorbol ester treatment induces association of PKC-␤II with actin-rich microfilaments in NIH 3T3 cells (Goodnight et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Translocation of protein kinase C‐βII in astrocytes requires organized actin cytoskeleton and is not accompanied by synchronous RACK1 relocation

Pascale¹,

Alkon²,

Grimaldi³

2004

Glia

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Protein kinase C (PKC)-betaII is the most abundant PKC isoform in astrocytes. Upon activation, this isoform of PKC translocates from the cytosol to the plasma membrane (PM). In this study, we investigated in astrocytes the modality of PKC-betaII translocation as far as the participation of the receptor for activated C kinase-1 (RACK1) and the requirement for intact cytoskeleton in the process. In astrocytes, Western blots and immunocytochemistry coupled to confocal microscopic quantitative analysis showed that after 5 min of phorbol-12-myristate-13-acetate (PMA) exposure, native PKC-betaII, but not PKC-betaI, is relocated efficiently from the cytosol to the PM. Translocation of PKC-betaII was not associated with synchronous RACK1 relocation. Furthermore, the quantity of PM-associated PKC-betaII that co-immunoprecipitated with PM-bound RACK1 increased following PMA exposure, indicating a post activation binding of the two proteins in the PM. Because RACK1 and PKC-betaII relocation seemed not to be synchronous, we hypothesized that an intermediate interaction with the cytoskeleton was taking place. In fact, we were able to show that pharmacological disruption of actin-based cytoskeleton greatly deranged PKC-betaII translocation to the PM. The requirement for intact actin cytoskeleton was specific, because depolymerization of tubulin had no effect on the ability of the kinase to translocate to the PM. These results indicate that in astrocytes, RACK1 and PKC-betaII synchronous relocation is not essential for relocation of PKC-betaII to the PM. In addition, we show for the first time that the integrity of the actin cytoskeleton plays a specific role in PKC-betaII movements in these cells. We hypothesize that in glial cells, rapidly occurring changes of actin cytoskeleton arrangement may be involved in the fast reprogramming of PKC targeting to specific PM location to phosphorylate substrates in different cellular locations.

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Possible involvement of microfilaments in protein kinase C translocation

Cited by 26 publications

References 16 publications

Direct interorganellar transfer of iron from endosome to mitochondrion

Direct interorganellar transfer of iron from endosome to mitochondrion

cPKC-dependent Sequestration of Membrane-recycling Components in a Subset of Recycling Endosomes

Translocation of protein kinase C‐βII in astrocytes requires organized actin cytoskeleton and is not accompanied by synchronous RACK1 relocation

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