Signaling from the secretory granule to the nucleus: Uhmk1 and PAM
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ABSTRACT: 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.
ORGANISM(S): Mus musculus
PROVIDER: GSE22509 | GEO | 2010/06/23
SECONDARY ACCESSION(S): PRJNA128497
REPOSITORIES: GEO
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