Secretory granule to the nucleus: role of a multiply phosphorylated intrinsically unstructured domain.
Ontology highlight
ABSTRACT:
SUBMITTER: Rajagopal C
PROVIDER: S-EPMC2757974 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The number and importance of intrinsically disordered proteins (IUP), known to be involved in various human disorders, are growing rapidly. To test for the generalized implications of intrinsic disorders in proteins involved in Neurodegenerative diseases, disorder prediction tools have been applied to three datasets comprising of proteins involved in Huntington Disease (HD), Parkinson's disease (PD), Alzheimer's disease (AD). Results show, in general, proteins in disease datasets possess significantly enhanced intrinsic unstructuredness. Most of these disordered proteins in the disease datasets are found to be involved in neuronal activities, signal transduction, apoptosis, intracellular traffic, cell differentiation etc. Also these proteins are found to have more number of interactors and hence as the proportion of disorderedness (i.e., the length of the unfolded stretch) increased, the size of the interaction network simultaneously increased. All these observations reflect that, "Moonlighting" i.e. the contextual acquisition of different structural conformations (transient), eventually may allow these disordered proteins to act as network "hubs" and thus they may have crucial influences in the pathogenecity of neurodegenerative diseases.
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Project description:Neurons and endocrine cells package peptides in secretory granules (large dense-core vesicles) for storage and stimulated release. Studies of peptidylglycine alpha-amidating monooxygenase (PAM), an essential secretory granule membrane enzyme, revealed a pathway that can relay information from secretory granules to the nucleus, resulting in alterations in gene expression. The cytosolic domain (CD) of PAM, a type 1 membrane enzyme essential for the production of amidated peptides, is basally phosphorylated by U2AF homology motif kinase 1 (Uhmk1) and other Ser/Thr kinases. Proopiomelanocortin processing in AtT-20 corticotrope tumor cells was increased when Uhmk1 expression was reduced. Uhmk1 was concentrated in the nucleus, but cycled rapidly between nucleus and cytosol. Endoproteolytic cleavage of PAM releases a soluble CD fragment that localizes to the nucleus. Localization of PAM-CD to the nucleus was decreased when PAM-CD with phosphomimetic mutations was examined and when active Uhmk1 was simultaneously overexpressed. Membrane-tethering Uhmk1 did not eliminate its ability to exclude PAM-CD from the nucleus, suggesting that cytosolic Uhmk1 could cause this response. Microarray analysis demonstrated the ability of PAM to increase expression of a small subset of genes, including aquaporin 1 (Aqp1) in AtT-20 cells. Aqp1 mRNA levels were higher in wild-type mice than in mice heterozygous for PAM, indicating that a similar relationship occurs in vivo. Expression of PAM-CD also increased Aqp1 levels whereas expression of Uhmk1 diminished Aqp1 expression. The outlines of a pathway that ties secretory granule metabolism to the transcriptome are thus apparent.
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Project description:C-terminal binding proteins (CtBPs) are moonlighting proteins involved in nuclear transcriptional corepression and in Golgi membrane tubule fission. Structural information on CtBPs is available for their substrate-binding domain, responsible for transcriptional repressor recognition/binding, and for the nucleotide-binding domain, involved in NAD(H)-binding and dimerization. On the contrary, little is known about the structure of CtBP C-terminal region ( approximately 90 residues), hosting sites for post-translational modifications. In the present communication we apply a combined approach based on bioinformatics, nuclear magnetic resonance, circular dichroism spectroscopy, and small-angle X-ray scattering, and we show that the CtBP C-terminal region is intrinsically unstructured in the full-length CtBP and in constructs lacking the substrate- and/or the nucleotide-binding domains. The flexible nature of this protein region, and its structural transitions, may be instrumental for CtBP recognition and binding to diverse molecular partners.
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Project description:Neurons and endocrine cells package peptides in secretory granules (large dense core vesicles; LDCVs) for storage and stimulated release. Studies of PAM, an essential secretory granule membrane enzyme, revealed a pathway that can relay information from secretory granules to the nucleus, resulting in alterations in gene expression. The cytosolic domain of PAM, a type 1 membrane enzyme essential for the production of amidated peptides, is basally phosphorylated by Uhmk1 and other Ser/Thr kinases. Proopiomelanocortin processing in AtT-20 corticotrope tumor cells was increased when Uhmk1 expression was reduced. Uhmk1 was concentrated in the nucleus, but cycled rapidly between nucleus and cytosol. Endoproteolytic cleavage of PAM releases a soluble cytosolic domain (CD) fragment that localizes to the nucleus. Localization of PAM-CD to the nucleus was decreased when PAM-CD with phosphomimetic mutations was examined and when active Uhmk1 was simultaneously over-expressed. Membrane-tethering Uhmk1 did not eliminate its ability to exclude PAM-CD from the nucleus, suggesting that cytosolic Uhmk1 could cause this response. Microarray analysis demonstrated the ability of PAM to increase expression of a small subset of genes, including aquaporin 1 (Aqp1) in AtT-20 cells. Aqp1 mRNA levels were higher in wildtype mice than in mice heterozygous for PAM, indicating that a similar relationship occurs in vivo. Expression of PAM-CD also increased Aqp1 levels while expression of Uhmk1 diminished Aqp1 expression. The outlines of a pathway that ties secretory granule metabolism to the transcriptome are thus apparent. Three separate clones of AtT-20 mouse corticotrope tumor cells stably transfected with doxycycline-inducible rat PAM-1 (clones 14, 6_1, 6_2) were treated with cotrol or doxycycline medium for 48 hours. Total mRNA was isolated and hybridized to an Illumina MouseWG-6 v 2.0 whole genome BeadChip.
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Project description:Neurons and endocrine cells package peptides in secretory granules (large dense core vesicles; LDCVs) for storage and stimulated release. Studies of PAM, an essential secretory granule membrane enzyme, revealed a pathway that can relay information from secretory granules to the nucleus, resulting in alterations in gene expression. The cytosolic domain of PAM, a type 1 membrane enzyme essential for the production of amidated peptides, is basally phosphorylated by Uhmk1 and other Ser/Thr kinases. Proopiomelanocortin processing in AtT-20 corticotrope tumor cells was increased when Uhmk1 expression was reduced. Uhmk1 was concentrated in the nucleus, but cycled rapidly between nucleus and cytosol. Endoproteolytic cleavage of PAM releases a soluble cytosolic domain (CD) fragment that localizes to the nucleus. Localization of PAM-CD to the nucleus was decreased when PAM-CD with phosphomimetic mutations was examined and when active Uhmk1 was simultaneously over-expressed. Membrane-tethering Uhmk1 did not eliminate its ability to exclude PAM-CD from the nucleus, suggesting that cytosolic Uhmk1 could cause this response. Microarray analysis demonstrated the ability of PAM to increase expression of a small subset of genes, including aquaporin 1 (Aqp1) in AtT-20 cells. Aqp1 mRNA levels were higher in wildtype mice than in mice heterozygous for PAM, indicating that a similar relationship occurs in vivo. Expression of PAM-CD also increased Aqp1 levels while expression of Uhmk1 diminished Aqp1 expression. The outlines of a pathway that ties secretory granule metabolism to the transcriptome are thus apparent.
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