Abstract
We have cloned eIF4E from the marine mollusk, Aplysia californica. The sequence of eIF4E from Aplysia is more similar to vertebrate eIF4Es than to other invertebrate sequences. Aplysia eIF4E is encoded by two tissue-specific RNAs. Antibodies raised to the carboxyl terminus of eIF4E recognize a 29-kDa protein that can bind to 7-methyl-GTP caps. The phosphorylation site identified in mammalian eIF4E is conserved in the Aplysia homologue, and an Aplysia eIF4E fusion protein is phosphorylated well by both Aplysia protein kinase C isoforms. However, protein kinase C phosphorylates both Ser-207 and Thr-208 in vitro, while only Ser-207 is phosphorylated in vivo. We have confirmed that Ser-207 is phosphorylated in vivo by raising a phosphopeptide antibody to this site. This antibody will be useful in determining the signal transduction pathways leading to eIF4E phosphorylation in Aplysia.
Highlights
Synaptic strength is modulated in the short term by posttranslational modifications, such as protein phosphorylation, and in the long term by changes in gene expression
EIF4E, the subunit of the eIF4F initiation complex that binds directly to the 5Ј-7-methyl-G(5Ј)ppp(5Ј)N mRNA cap, from its complex with the eIF4E-binding protein (9 –11). eIF4E is regulated by phosphorylation at Ser-209 [12,13,14], increasing its ability to bind to caps [15] and to form the eIF4F complex [16, 17]
When 5-HT is applied only to the synaptic region, long term facilitation requires local protein synthesis at the synapse [24]. 5-HT increases the rate of translation in sensory neurons and in the entire pleural ganglia [25, 26]. 5-HT-mediated activation of translation in the pleural ganglia can be blocked by rapamycin [26], suggesting that it may involve regulation of eIF4E
Summary
Synaptic strength is modulated in the short term by posttranslational modifications, such as protein phosphorylation, and in the long term by changes in gene expression. In other cell types growth factors increase the translation rate through a rapamycin-sensitive pathway involving phosphorylation of two regulators of translation, the S6 kinase and the eukaryotic initiation factor 4E (eIF4E)-binding protein [7,8,9]. In Vitro Phosphorylation—The His-eIF4E fusion protein was tested as a substrate for phosphorylation by purified AplI and AplII, the two Aplysia PKC isoforms [29, 30].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
