Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.12 (PKG)
 2,515 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The septins are a family of GTPase enzymes, some of which are required for the cytokinesis stage of cell division and others of which are associated with exocytosis. We purified and cloned the cDNA for a 40-kDa protein from rat brain that is a substrate for type I cGMP-dependent protein kinase (PKG). The amino acid sequences of two tryptic peptides of P40 showed high homology to the septins. Molecular cloning revealed the 358-amino acid P40 to be a new member of the septin family. P40 was named G-septin, as it is phosphorylated in vitro by PKG, but relatively poorly by the related cAMP-dependent protein kinase and not by protein kinase C. Two splice variants of G-septin (alpha and beta) were found with distinct N and C termini, but a common GTPase domain. G-septin lacks the C-terminal coiled-coil domain characteristic of all other mammalian septins and uniquely has two predicted phosphorylation site motifs for type I PKG. Photoaffinity labeling with [alpha-(32)P]GTP confirmed that G-septin is a GTP-binding protein. Northern blotting showed that G-septin mRNA (5.0 kilobases) is highly expressed in brain and undetectable in 12 other tissues, indicating that the G-septins are primarily neuronal proteins. Very low levels of 6.0-, 3.4-, and 2.6-kilobase transcripts were found in testis. Our results reveal a new class of brain-specific septins that may be regulated by PKG in neurons.
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PMID:Phosphorylation of a new brain-specific septin, G-septin, by cGMP-dependent protein kinase. 1074 83

The septins are a family of GTPase enzymes required for cytokinesis and play a role in exocytosis. Among the ten vertebrate septins, Sept5 (CDCrel-1) and Sept3 (G-septin) are primarily concentrated in the brain, wherein Sept3 is a substrate for PKG-I (cGMP-dependent protein kinase-I) in nerve terminals. There are two motifs for potential PKG-I phosphorylation in Sept3, Thr-55 and Ser-91, but phosphoamino acid analysis revealed that the primary site is a serine. Derivatization of phosphoserine to S-propylcysteine followed by N-terminal sequence analysis revealed Ser-91 as a major phosphorylation site. Tandem MS revealed a single phosphorylation site at Ser-91. Substitution of Ser-91 with Ala in a synthetic peptide abolished phosphorylation. Mutation of Ser-91 to Ala in recombinant Sept3 also abolished PKG phosphorylation, confirming that Ser-91 is the major site in vitro. Antibodies raised against a peptide containing phospho-Ser-91 detected phospho-Sept3 only in the cytosol of nerve terminals, whereas Sept3 was located in a peripheral membrane extract. Therefore Sept3 is phosphorylated on Ser-91 in nerve terminals and its phosphorylation may contribute to the regulation of its subcellular localization in neurons.
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PMID:Phosphorylation of septin 3 on Ser-91 by cGMP-dependent protein kinase-I in nerve terminals. 1510 17

Septins constitute a family of conserved proteins that are required for cytokinesis in a wide range of organisms. Most cells express a set of septin proteins and these are found to assemble into hetero-oligomeric septin complexes that appear filamentous. However, the mechanisms controlling the function and polymerization of septins are not known. We therefore examined the possibility that septins could be post-translationally modified by phosphorylation. We present herein a combined theoretical and experimental approach for the analysis of Septin 2 (Sept2) monophosphorylation in vivo. We purified and characterized the human recombinant Sept2, a 45-kDa protein, expressed from Sf21 insect cells. Analysis by matrix-assisted laser desorption/ionization quadrupole time-of-flight mass spectrometry on the full-length protein sequence of wild-type Sept2 revealed a unique phosphorylation site at residue Ser248 in vivo, which is consistent with one of the twelve phosphorylation sites in the protein sequence theoretically predicted by the Netphos program. Additional predictions with the motif scan programs Scansite and Prosite suggest that the phosphorylation of wild-type Sept2 might be a potential substrate for casein kinase 2. Site-directed mutagenesis of residue 248 from serine to alanine abrogated this phosphorylation. The location of phosphorylation in Sept2 differs from the sites predicted for cGMP-dependent protein kinase (PKG) phosphorylation in Septin 3, raising the possibility that different septins may undergo distinct phosphorylation events that could control their functions in important cellular processes such as neurotransmission or cytokinesis.
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PMID:Septin 2 phosphorylation: theoretical and mass spectrometric evidence for the existence of a single phosphorylation site in vivo. 1515 Aug 37

The septins are GTPase enzymes with multiple roles in cytokinesis, cell polarity or exocytosis. The proteins from the mammalian septin genes are called Sept1-10. Most are expressed in multiple tissues, but the mRNA for Sept5 (CDCrel-1) and Sept3 (G-septin) appear to be primarily expressed in brain. Sept3 is phosphorylated by cGMP-dependent protein kinase I (PKG-I) and the cGMP/PKG pathway is involved in presynaptic plasticity. Therefore to determine whether Sept3 specifically associates with neurones and nerve terminals we investigated its distribution in rat brain and neuronal cultures. Sept3 protein was detected only in brain by immunoblot, but not in 12 other tissues examined. Levels were high in all adult brain regions, and reduced in those enriched in white matter. Expression was developmentally regulated, being absent in the early embryo, low in late embryonic rat brain and increasing after birth. Like dynamin I, Sept3 was specifically enriched in synaptosomes compared with whole brain, and was only found in a peripheral membrane extract and not in the soluble or membrane extracts. Sept3 was particularly abundant in mossy fibre nerve terminals in the hippocampus. In primary cultured hippocampal neurones Sept3 immunoreactivity was punctate in neurites and predominantly localized to presynaptic terminals, strongly colocalizing with synaptophysin and dynamin I. The specific nerve terminal localization was confirmed by immunogold electron microscopy. Together this shows that Sept3 is a neurone-specific protein highly enriched in nerve terminals which supports a secretory role in synaptic vesicle recycling.
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PMID:Septin 3 (G-septin) is a developmentally regulated phosphoprotein enriched in presynaptic nerve terminals. 1548 89