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Neurotrophin regulation of beta-actin mRNA and protein localization within growth cones.

Zhang HL, Singer RH, Bassell GJ - J. Cell Biol. (1999)

Bottom Line: NT-3 treatment resulted in a rapid and transient stimulation of PKA activity that preceded the localization of beta-actin mRNA.Depolymerization of microtubules, but not microfilaments, inhibited the NT-3-induced localization of beta-actin mRNA.These results suggest that NT-3 activates a cAMP-dependent signaling mechanism to promote the microtubule-dependent localization of beta-actin mRNA within growth cones.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.

ABSTRACT
Neurotrophins play an essential role in the regulation of actin-dependent changes in growth cone shape and motility. We have studied whether neurotrophin signaling can promote the localization of beta-actin mRNA and protein within growth cones. The regulated localization of specific mRNAs within neuronal processes and growth cones could provide a mechanism to modulate cytoskeletal composition and growth cone dynamics during neuronal development. We have previously shown that beta-actin mRNA is localized in granules that were distributed throughout processes and growth cones of cultured neurons. In this study, we demonstrate that the localization of beta-actin mRNA and protein to growth cones of forebrain neurons is stimulated by neurotrophin-3 (NT-3). A similar response was observed when neurons were exposed to forskolin or db-cAMP, suggesting an involvement of a cAMP signaling pathway. NT-3 treatment resulted in a rapid and transient stimulation of PKA activity that preceded the localization of beta-actin mRNA. Localization of beta-actin mRNA was blocked by prior treatment of cells with Rp-cAMP, an inhibitor of cAMP-dependent protein kinase A. Depolymerization of microtubules, but not microfilaments, inhibited the NT-3-induced localization of beta-actin mRNA. These results suggest that NT-3 activates a cAMP-dependent signaling mechanism to promote the microtubule-dependent localization of beta-actin mRNA within growth cones.

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Stimulation of β-actin mRNA levels in neurons treated with NT-3, forskolin, or serum. Northern blot hybridization with 32P-labeled cDNA probes to β-actin mRNA (see Materials and Methods). An increase in β-actin mRNA levels occurred at 30 min which was after the relocalization of β-actin mRNA to growth cones.
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Figure 10: Stimulation of β-actin mRNA levels in neurons treated with NT-3, forskolin, or serum. Northern blot hybridization with 32P-labeled cDNA probes to β-actin mRNA (see Materials and Methods). An increase in β-actin mRNA levels occurred at 30 min which was after the relocalization of β-actin mRNA to growth cones.

Mentions: The localization of β-actin mRNA to growth cones in response to neurotrophin signaling is suggestive of a mechanism that promotes a redistribution in the preexisting mRNA population. In addition, neurotrophins may also enhance β-actin gene transcription that would result in increased levels of mRNA in the cytoplasm. We evaluated β-actin mRNA levels by Northern blot analysis in normal, starved, and stimulated cultures (Fig. 10). Starvation of cells for 6 h resulted in a 52% decrease in β-actin mRNA levels. Treatment of starved cells with NT-3, forskolin, or fetal bovine serum (also promotes mRNA localization, data not shown) did not result in an increase in β-actin mRNA levels within the 10-min time period during which mRNA localization occurred. These results suggest that mRNA localization can be due to a rapid redistribution of preexisting mRNAs. A 30-min treatment with NT-3 did result in an increase in β-actin mRNA levels (Fig. 9) which then declined at 2 h (not shown). These results indicate that neurotrophin signals can also upregulate β-actin mRNA levels, and that this response may be one of the last events in a signal transduction cascade that collectively affects many aspects of actin gene expression and localization which include actin polymerization, localization of β-actin mRNA and protein, and perhaps transcriptional activation.


Neurotrophin regulation of beta-actin mRNA and protein localization within growth cones.

Zhang HL, Singer RH, Bassell GJ - J. Cell Biol. (1999)

Stimulation of β-actin mRNA levels in neurons treated with NT-3, forskolin, or serum. Northern blot hybridization with 32P-labeled cDNA probes to β-actin mRNA (see Materials and Methods). An increase in β-actin mRNA levels occurred at 30 min which was after the relocalization of β-actin mRNA to growth cones.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2164987&req=5

Figure 10: Stimulation of β-actin mRNA levels in neurons treated with NT-3, forskolin, or serum. Northern blot hybridization with 32P-labeled cDNA probes to β-actin mRNA (see Materials and Methods). An increase in β-actin mRNA levels occurred at 30 min which was after the relocalization of β-actin mRNA to growth cones.
Mentions: The localization of β-actin mRNA to growth cones in response to neurotrophin signaling is suggestive of a mechanism that promotes a redistribution in the preexisting mRNA population. In addition, neurotrophins may also enhance β-actin gene transcription that would result in increased levels of mRNA in the cytoplasm. We evaluated β-actin mRNA levels by Northern blot analysis in normal, starved, and stimulated cultures (Fig. 10). Starvation of cells for 6 h resulted in a 52% decrease in β-actin mRNA levels. Treatment of starved cells with NT-3, forskolin, or fetal bovine serum (also promotes mRNA localization, data not shown) did not result in an increase in β-actin mRNA levels within the 10-min time period during which mRNA localization occurred. These results suggest that mRNA localization can be due to a rapid redistribution of preexisting mRNAs. A 30-min treatment with NT-3 did result in an increase in β-actin mRNA levels (Fig. 9) which then declined at 2 h (not shown). These results indicate that neurotrophin signals can also upregulate β-actin mRNA levels, and that this response may be one of the last events in a signal transduction cascade that collectively affects many aspects of actin gene expression and localization which include actin polymerization, localization of β-actin mRNA and protein, and perhaps transcriptional activation.

Bottom Line: NT-3 treatment resulted in a rapid and transient stimulation of PKA activity that preceded the localization of beta-actin mRNA.Depolymerization of microtubules, but not microfilaments, inhibited the NT-3-induced localization of beta-actin mRNA.These results suggest that NT-3 activates a cAMP-dependent signaling mechanism to promote the microtubule-dependent localization of beta-actin mRNA within growth cones.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.

ABSTRACT
Neurotrophins play an essential role in the regulation of actin-dependent changes in growth cone shape and motility. We have studied whether neurotrophin signaling can promote the localization of beta-actin mRNA and protein within growth cones. The regulated localization of specific mRNAs within neuronal processes and growth cones could provide a mechanism to modulate cytoskeletal composition and growth cone dynamics during neuronal development. We have previously shown that beta-actin mRNA is localized in granules that were distributed throughout processes and growth cones of cultured neurons. In this study, we demonstrate that the localization of beta-actin mRNA and protein to growth cones of forebrain neurons is stimulated by neurotrophin-3 (NT-3). A similar response was observed when neurons were exposed to forskolin or db-cAMP, suggesting an involvement of a cAMP signaling pathway. NT-3 treatment resulted in a rapid and transient stimulation of PKA activity that preceded the localization of beta-actin mRNA. Localization of beta-actin mRNA was blocked by prior treatment of cells with Rp-cAMP, an inhibitor of cAMP-dependent protein kinase A. Depolymerization of microtubules, but not microfilaments, inhibited the NT-3-induced localization of beta-actin mRNA. These results suggest that NT-3 activates a cAMP-dependent signaling mechanism to promote the microtubule-dependent localization of beta-actin mRNA within growth cones.

Show MeSH
Related in: MedlinePlus