Bidirectional pigment granule movements of melanophores are regulated by protein phosphorylation and dephosphorylation

Rozdzial, Moshe M.; Haimo, Leah T.

doi:10.1016/0092-8674(86)90821-4

Cited by 151 publications

(81 citation statements)

References 51 publications

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“…There is abundant evidence that in melanophores high levels of intracellular cAMP acts through PKA to induce pigment granule dispersion (11,40), and there is equally compelling data implicating phosphatase activity as the mechanism that triggers pigment aggregation (9,12,41). The molecular targets of this cyclic phosphorylation remain unidentified, however, as does an understanding of how this phosphorylation modulates motor activity.…”

Section: Discussionmentioning

confidence: 99%

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Regulated bidirectional motility of melanophore pigment granules along microtubules in vitro

Rogers

Tint

Fanapour

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

210

189

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Although many types of membrane-bound organelles rely upon microtubule-based transport for their proper placement within the cytoplasm, the molecular mechanisms that regulate intracellular motility remain largely unknown. To address this problem, we have studied the microtubule-dependent dispersion and aggregation of pigment granules from an immortalized Xenopus melanophore cell line. We have reconstituted pigment granule motility along bovine brain microtubules in vitro using a microscopebased motility assay. Pigment granules, or melanosomes, move along single microtubules bidirectionally; however, analysis of the polarities of this movement shows that melanosomes that have been purified from dispersed cells exhibit mostly plus end-directed motility, while movement of organelles from aggregating cells is biased toward the minus end. Removal of all soluble proteins from the melanosome fractions by density gradient centrifugation does not diminish organelle motility, demonstrating that all the components required for transport have a stable association with the melanosome membranes. Western blotting shows the presence of the plus end-directed motor, kinesin-II, and the minus end-directed motor, cytoplasmic dynein in highly purified melanosomes. Therefore, purified melanosomes retain their ability to move along microtubules as well as their regulated state. Direct biochemical comparison of melanosomes from aggregated and dispersed cells may elucidate the molecular mechanisms that regulate organelle transport in melanophores.

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Section: Discussionmentioning

confidence: 99%

“…9 and 10). Conversely, a decrease of cAMP levels within the cell permits an as yet unidentified phosphatase to trigger pigment aggregation (11,12). It is unknown whether the motors responsible for pigment transport are phosphorylated directly by PKA or are downstream in a multistep pathway.…”

mentioning

confidence: 99%

Regulated bidirectional motility of melanophore pigment granules along microtubules in vitro

Rogers

Tint

Fanapour

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

210

189

View full text Add to dashboard Cite

show abstract

“…Removal of these phosphates has effects on the ATPase activity of this dynein. In fish melanophores and xanthophores, pharmacological and other studies on pigment granule transport demonstrate that the movement of the pigment granules along microtubules between aggregated and dispersed states is regulated by phosphorylation (34,35,53,65). In particular, protein dephosphorylation is necessary for MT-minus end directed (retrograde) motility (34,35,53,65).…”

Section: Discussionmentioning

confidence: 99%

“…Protein phos-phorylation regulates a wide range of cellular processes (71) and experimental evidence implicates phosphorylation in the regulation of numerous microtubule-based motile systems (6,14,22,29,35,54,63,65). Considerable evidence indicates that phosphorylation regulates the movement of pigment granules along microtubules in fish pigment cells (34,35,53,54,65). It has recently been shown that the anterograde motor, kinesin, is phosphorylated in vivo, and in vitro experiments suggest that phosphorylation may regulate kinesin function (26,37,55).…”

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confidence: 99%

Differential phosphorylation in vivo of cytoplasmic dynein associated with anterogradely moving organelles.

Dillman

Pfister

1994

The Journal of Cell Biology

172

187

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Abstract. Two microtubule-stimulated ATPases, cytoplasmic dynein, and kinesin, are believed to be responsible for the intracellular movement of membrane-bound organelles in opposite directions along microtubules. An unresolved component of this model is the mechanism by which cells regulate these two motors to direct various membrane-bound organelles to their proper locations. To determine if phosphorylation may play a role in the regulation of cytoplasmic dynein, the in vivo phosphorylation state of cytoplasmic dynein from two cellular pools was examined. The entire cellular pool of brain cytoplasmic dynein was metabolically labeled by the infusion of [32P]orthophosphate into the cerebrospinal fluid of rat brain ventricles. To characterize the phosphorylation of dynein associated with anterograde membranebound organelles, the optic nerve fast axonal transport system was used. Using a monoclonal antibody to the 74-kD polypeptide of brain cytoplasmic dynein, the native dynein complex was immunoprecipitated from the radiolabeled tissue extracts. Autoradiographs of one and two dimensional gels showed labeling of nearly all of the polypeptide isoforms of cytoplasmic dynein from rat brain. These polypeptides are phosphorylated on serine residues. Comparison of the amount of 32p incorporated into the dynein polypeptides revealed differences in the phosphorylation of dynein polypeptides from the anterograde and the cellular pools. Most interestingly, the 530-kD heavy chain of dynein appears to be phosphorylated to a lesser extent in the anterograde pool than in the cellular pool. Since the anterograde pool contains inactive dynein, while the entire cellular pool contains both inactive and active dynein, these results are consistent with the hypothesis that phosphorylation regulates the functional activity of cytoplasmic dynein.

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“…Pigment organelles can be distributed in the cells in two configurations: either aggregated in the perinuclear region or homogeneously dispersed in the cytoplasm. The transport of pigment organelles during aggregation and dispersion is regulated by signaling mechanisms initiated by the binding of specific hormones to cell surface receptors [29]. In a recent paper, we analyzed the MSD dependence with the time lag using an empirical model [13].…”

Section: Introductionmentioning

confidence: 99%

Transition to superdiffusive behavior in intracellular actin-based transport mediated by molecular motors

Bruno

Levi

Brunstein³

et al. 2009

Phys. Rev. E

119

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Intracellular transport of large cargoes, such as organelles, vesicles or large proteins, is a complex dynamical process that involves the interplay of ATP-consuming molecular motors, cytoskeleton filaments and the viscoelastic cytoplasm. The displacements of particles or probes in the cell cytoplasm as a function of time are characterized by different (anomalous) diffusion regimes. We investigate here the motion of pigment organelles (melanosomes) driven by myosin-V motors in Xenopus laevis melanocytes using a high spatio-temporal resolution tracking technique. By analyzing the mean square displacement (MSD) of the obtained trajectories as a function of the time lag, we show that the melanosomes display a transition between subdiffusive to superdiffusive behavior. A stochastic theoretical model is introduced to generalize the interpretation of our data. Starting from a generalized Langevin equation that explicitly considers the collective action of the molecular motors we derive an analytical expression for the MSD as a function of the time lag, which also takes into account the experimental noise. By fitting our model to the experimental data we were able to discriminate the exponents that characterize the passive and active contributions to melanosome dynamics. The model also estimates the "global" motor forces correctly. In this sense, our model gives a quantitative description of active transport in living cells with a reduced number of parameters.

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Bidirectional pigment granule movements of melanophores are regulated by protein phosphorylation and dephosphorylation

Cited by 151 publications

References 51 publications

Regulated bidirectional motility of melanophore pigment granules along microtubules in vitro

Regulated bidirectional motility of melanophore pigment granules along microtubules in vitro

Differential phosphorylation in vivo of cytoplasmic dynein associated with anterogradely moving organelles.

Transition to superdiffusive behavior in intracellular actin-based transport mediated by molecular motors

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