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Statistics of active transport in Xenopus melanophores cells.

ABSTRACT: The transport of cell cargo, such as organelles and protein complexes in the cytoplasm, is determined by cooperative action of molecular motors stepping along polar cytoskeletal elements. Analysis of transport of individual organelles generated useful information about the properties of the motor proteins and underlying cytoskeletal elements. In this work, for the first time (to our knowledge), we study collective movement of multiple organelles using Xenopus melanophores, pigment cells that translocate several thousand of pigment granules (melanosomes), spherical organelles of a diameter of ?1 ?m. These cells disperse melanosomes in the cytoplasm in response to high cytoplasmic cAMP, while at low cAMP melanosomes cluster at the cell center. Obtained results suggest spatial and temporal organization, characterized by strong correlations between movement of neighboring organelles, with correlation length of ?4 ?m and pair lifetime ?5 s. Furthermore, velocity statistics revealed strongly non-Gaussian velocity distribution with high velocity tails demonstrating exponential behavior suggestive of strong velocity correlations. Depolymerization of vimentin intermediate filaments using a dominant-negative vimentin mutant or actin with cytochalasin B reduced correlation of behavior of individual particles. Based on our analysis, we concluded that steric repulsion is dominant, but both intermediate filaments and actin microfilaments are involved in dynamic cross-linking organelles in the cytoplasm.

SUBMITTER: Snezhko A

PROVIDER: S-EPMC2980738 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Statistics of active transport in Xenopus melanophores cells.

Snezhko Alexey A Barlan Kari K Aranson Igor S IS Gelfand Vladimir I VI

Biophysical journal 20101101 10

The transport of cell cargo, such as organelles and protein complexes in the cytoplasm, is determined by cooperative action of molecular motors stepping along polar cytoskeletal elements. Analysis of transport of individual organelles generated useful information about the properties of the motor proteins and underlying cytoskeletal elements. In this work, for the first time (to our knowledge), we study collective movement of multiple organelles using Xenopus melanophores, pigment cells that tra ...[more]

PMID: 21081069

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Project description:Melatonin (5-methoxy N-acetyltryptamine) and serotonin (5-HT) exert rapid, but opposite effects on pigment granule distribution in Xenopus laevis melanophores. Low concentrations of melatonin (10(-11) - 10(-9) M) cause a dramatic perinuclear aggregation of the melanin-containing granules, while 5-HT (10(-8) - 10(-5) M) disperses pigment granules throughout the cell. The present study found that pharmacological doses of melatonin (> or =10(-6) M) induced a time- and concentration-dependent pigment granule dispersion, which was mediated by an endogenous melanophore 5-HT receptor. 5-HT produced a concentration-dependent elevation of melanophore cyclic AMP, and 5-HT-induced dispersion was blocked by H89 (10(-4) M), an inhibitor of protein kinase A (PKA), but not by a PKC inhibitor (Ro 31-8220, 10(-5) M), indicating a vital role for cyclic AMP in 5-HT-induced dispersion. 5-HT-mediated dispersion was not blocked by antagonists selective for G(s)-coupled 5-HT(4) (GR113808) or 5-HT(6) (Ro 04-6790, Ro 63-0563, olanzepine) receptors, nor by 5-HT(1 - 3) (pindolol, ketanserine, metoclopramide, MDL72222, tropisetron) receptor antagonists, but was inhibited by a selective 5-HT(7) receptor antagonist, DR4004, and other antagonists with a high affinity for 5-HT(7) receptors. The rank order of antagonist potency was: risperidone (mean pK(B) 7.82)>methiothepin (7.43)>DR4004 (6.92)>mesulergine (6.83)>methysergide (6.60)>[+/-]-sulpiride (5.81)>spiperone (5.52). The agonist potency order [mean pEC(50), 5-CT (8.68)>5-HT (7.13)>5-MT (6.94)>8-OH-DPAT (4.79)>sumatriptan (<4)] was also consistent with an action on 5-HT(7) receptors. RT - PCR confirmed that melanophores express 5-HT(7) receptor mRNA. The pigment dispersing effect of high melatonin concentrations in melanophores is most likely mediated by activation of 5-HT(7) receptors. Conceivably some of the effects attributed to pharmacological doses of melatonin in mammals may be mediated by activation of 5-HT(7) receptors.

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Statistics of active transport in Xenopus melanophores cells.

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Statistics of active transport in Xenopus melanophores cells.

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