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Results for “Protein Isoforms”

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PubMed2006

A-to-I pre-mRNA editing of the serotonin 2C receptor: comparisons among inbred mouse strains.

The serotonin receptor 5HT2CR pre-mRNA is subject to adenosine deamination (RNA editing) at five residues located within a 15 nucleotide stretch of the coding region. Such changes of adenosine to inosine (A-to-I) can produce 32 mRNA variants, encoding 24 different protein isoforms, some of which vary in biochemical and pharmacological properties. Because serotonin mediates diverse neurological processes relevant to behavior and because inbred mouse strains vary in their responses to tests of learning and behavior, we have examined the A-to-I editing patterns of the 5HT2CR mRNA in whole brains from eight mouse strains. By sequencing approximately 100 clones from individual mice, we generated detailed information on levels of editing at each site and patterns of editing that identify a total of 28 mRNA and 20 protein isoforms. Significant differences between individuals from different strains were found in total editing frequency, in the proportion of transcripts with 1 and 4 edited sites, in editing frequency at the A, B, E and D sites, in amino acid frequencies at positions 157 and 161, and in subsets of major protein isoforms. Primer extension assays were used to show that individuals within strains (six C3H.B-+rd1 and four 129SvImrJ) displayed no significant differences in any feature. These findings suggest that genetic background contributes to subtle variation in 5HT2CR mRNA editing patterns which may have consequences for pharmacological treatments and behavioral testing.

Adenosine↗

PubMed1999

A nonerythroid isoform of protein 4.1R interacts with the nuclear mitotic apparatus (NuMA) protein.

Red blood cell protein 4.1 (4.1R) is an 80- kD erythrocyte phosphoprotein that stabilizes the spectrin/actin cytoskeleton. In nonerythroid cells, multiple 4.1R isoforms arise from a single gene by alternative splicing and predominantly code for a 135-kD isoform. This isoform contains a 209 amino acid extension at its NH2 terminus (head piece; HP). Immunoreactive epitopes specific for HP have been detected within the cell nucleus, nuclear matrix, centrosomes, and parts of the mitotic apparatus in dividing cells. Using a yeast two-hybrid system, in vitro binding assays, coimmunolocalization, and coimmunoprecipitation studies, we show that a 135-kD 4.1R isoform specifically interacts with the nuclear mitotic apparatus (NuMA) protein. NuMA and 4.1R partially colocalize in the interphase nucleus of MDCK cells and redistribute to the spindle poles early in mitosis. Protein 4.1R associates with NuMA in the interphase nucleus and forms a complex with spindle pole organizing proteins, NuMA, dynein, and dynactin during cell division. Overexpression of a 135-kD isoform of 4.1R alters the normal distribution of NuMA in the interphase nucleus. The minimal sequence sufficient for this interaction has been mapped to the amino acids encoded by exons 20 and 21 of 4.1R and residues 1788-1810 of NuMA. Our results not only suggest that 4.1R could, possibly, play an important role in organizing the nuclear architecture, mitotic spindle, and spindle poles, but also could define a novel role for its 22-24-kD domain.

Amino Acid Sequence↗

PubMed2005

Use of surface-enhanced laser desorption ionization-time-of-flight to identify heat shock protein 70 isoforms in closely related species of the virilis group of Drosophila.

The 70-kDa heat shock protein (Hsp) family in all Drosophila species includes 2 environmentally inducible family members, Hsp70 and Hsp68. Two-dimensional gel electrophoresis revealed an unusual pattern of heat shock-inducible proteins in the species of the virilis group. Trypsin fingerprinting and microsequencing of tryptic peptides using ProteinChip Array technology identified the major isoelectric variants of Hsp70 family, including Hsp68 isoforms that differ in both molecular mass and isoelectric point from those in Drosophila melanogaster. The peculiar electrophoretic mobility is consistent with the deduced amino acid sequence of corresponding hsp genes from the species of the virilis group.

Animals↗

PubMed2000

Localization of cGMP-dependent protein kinase isoforms in mouse eye.

PURPOSE: To examine the expression of the major isoforms of cyclic guanosine monophosphate (cGMP)-dependent protein kinase (cGK) in mouse eye. METHODS: Immunohistochemical localization of cGMP in mouse eye cryosections was performed using an anti-cGMP antibody, followed by visualization with indirect fluorescence microscopy. The presence of types Ialpha, Ibeta, and II cGK mRNAs in mouse eye extracts was determined initially by RNase protection analysis. Further localization of cGK I and II mRNAs on cryosections was accomplished by in situ hybridization using digoxigenin-labeled cRNA probes and an alkaline phosphatase-conjugated anti-digoxigenin antibody. Finally, cGK I protein was localized to subcellular areas within the retina using an anti-cGK I-specific primary antibody. RESULTS: In initial immunohistochemical experiments cGMP was present in numerous regions and layers within the eye and retina. Subsequent RNase protection studies demonstrated that cGK Ialpha, Ibeta, and II mRNAs were present in mouse eye and that type Ibeta mRNA were 6.6 and 30 times more abundant than type Ialpha and type II, respectively. By in situ hybridization, cGK I mRNA was localized to photoreceptor inner segments and the ganglion cell and inner nuclear layers of the retina, and lesser amounts were found in the ciliary epithelium, lens, and cornea. The cGK II mRNA expression pattern was similar but not identical with that of cGK I. Finally, within the retina, cGK I protein was most abundant in the inner plexiform layer, with significant amounts in ganglion cells and photoreceptor inner segments as well. CONCLUSIONS: The presence of these cGK isoforms in discrete areas throughout the eye suggests multiple roles for the cGMP-dependent signal transduction system in the regulation of physiologic and pathologic ocular processes.

Animals↗

PubMed2003

Complement regulation by Kaposi's sarcoma-associated herpesvirus ORF4 protein.

Kaposi's sarcoma-associated herpesvirus (KSHV) is associated with three types of human tumor: Kaposi's sarcoma, multicentric Castleman's disease, and primary effusion lymphoma. The virus encodes a number of proteins that participate in disrupting the immune response, one of which was predicted by sequence analysis to be encoded by open reading frame 4 (ORF4). The predicted ORF4 protein shares homology with cellular proteins referred to as regulators of complement activation. In the present study, the transcription profile of the ORF4 gene was characterized, revealing that it encodes at least three transcripts, by alternative splicing mechanisms, and three protein isoforms. Functional studies revealed that each ORF4 protein isoform inhibits complement and retains a C-terminal transmembrane domain. Consistent with the complement-regulating activity, we propose to name the proteins encoded by the ORF4 gene collectively as KSHV complement control protein (KCP). KSHV ORF4 is the most complex alternatively spliced gene encoding a viral complement regulator described to date. KCP inhibits the complement component of the innate immune response, thereby possibly contributing to the in vivo persistence and pathogenesis of this virus.

Alternative Splicing↗

PubMed2006

Identification and expression analysis of alternative splice variants of the rat Hax-1 gene.

Hax-1 protein, which has been studied in mice and humans, shows a potent anti-apoptotic activity and is involved in regulation of cell motility. Cloning of the rat Hax-1 cDNA has revealed seven alternative transcripts, which differ mostly in their 5' region. Alternative splicing concerns exon 1, skipped in 5 transcripts, intron 1 which is partially retained in these transcripts, exon 2, which can be partially skipped, and intron 2, retained in one variant. The existence of different splicing variants was confirmed by exon-junction-specific RT-PCR and RNase protection assay. Analysis of expression indicates that overall Hax-1 mRNA level is relatively low in most tissues and very high in testes, and that the expression pattern of the variants is similar in different tissues. Presence of different transcripts implies the existence of several protein isoforms, with three putative start codons. The existence of at least three protein isoforms was confirmed by Western blot. Interestingly, high mRNA level in testes does not translate into high protein level, suggesting the existence of tissue-specific translational regulation or regulated protein degradation.

Alternative Splicing↗

PubMed2006

Mechanism of action of sulforaphane: inhibition of p38 mitogen-activated protein kinase isoforms contributing to the induction of antioxidant response element-mediated heme oxygenase-1 in human hepatoma HepG2 cells.

Exposure of sulforaphane to HepG2 cells increased heme oxygenase-1 (HO-1) expression by activating antioxidant response element (ARE) through induction of Nrf2 and suppression of Kelch-like ECH-associated protein 1 (Keap1). Using human HO-1 promoter reporter plasmids and ChIP assay, we have identified that sulforaphane transcriptionally activated the upstream ARE-rich enhancer region, located at -9.0 kb upstream human HO-1 promoter. Induction of HO-1 by sulforaphane was attenuated by overexpression of mutant Nrf2 plasmid in HepG2 cells and totally abolished in Nrf2 knockout mouse embryonic keratinocytes and fibroblasts. Overexpression of individual p38 mitogen-activated protein (MAP) kinase (MAPK) isoforms also suppressed constitutive as well as sulforaphane- or Nrf2-induced ARE-dependent gene expression. Among the upstream kinases, although MKK3 was not involved in suppression of ARE by any of p38 MAPK isoforms, MKK6 selectively suppressed ARE by p38 gamma or p38 delta, but not by p38 alpha or p38 beta. Importantly, sulforaphane not only activated MAP/extracellular signal-regulated kinase (ERK) kinases 1/2 and ERK1/2, but also strongly suppressed anisomycin-induced activation of p38 MAPK isoforms by blocking phosphorylation of upstream kinases, MKK3/6. Finally, we found that stimulation of p38 MAPK isoforms phosphorylated purified Nrf2 protein and caused an increase in the interaction between Nrf2 and Keap1 in vitro and the suppression of Nrf2 translocation into the nucleus. Collectively, our results indicate that transcriptional activation of Nrf2/ARE is critical in sulforaphane-mediated induction of HO-1, which can be modulated in part by the blockade of p38 MAPK signaling pathway. In addition, our study shows that p38 MAPK can phosphorylate Nrf2 and promotes the association between Nrf2 and Keap1 proteins, thereby potentially inhibiting nuclear translocation of Nrf2.

Animals↗

PubMed2004

Critical role of the atypical {lambda} isoform of protein kinase C (PKC-{lambda}) in oxidant-induced disruption of the microtubule cytoskeleton and barrier function of intestinal epithelium.

Oxidant injury to epithelial cells and gut barrier disruption are key factors in the pathogenesis of inflammatory bowel disease. Studying monolayers of intestinal (Caco-2) cells, we reported that oxidants disrupt the cytoskeleton and cause barrier dysfunction (hyperpermeability). Because the lambda isoform of protein kinase C (PKC-lambda), an atypical diacylglycerol-independent isozyme, is abundant in parental (wild type) Caco-2 cells and is translocated to the particulate fractions upon oxidant exposure, we hypothesized that PKC-lambda is critical to oxidative injury to the assembly and architecture of cytoskeleton and the intestinal barrier function. To this end, Caco-2 cells were transfected with an inducible plasmid, a tetracycline-responsive system, to create novel clones stably overexpressing native PKC-lambda. Other cells were transfected with a dominant-negative plasmid to stably inhibit the activity of native PKC-lambda. Cells were exposed to oxidant (H(2)O(2)) +/- modulators. Parental Caco-2 cells were treated similarly. We then monitored barrier function (fluorescein sulfonic acid clearance), microtubule cytoskeletal stability (confocal microscopy, immunoblotting), subcellular distribution of PKC-lambda (immunofluorescence, immunoblotting, immunoprecipitation), and PKC-lambda isoform activity (in vitro kinase assay). Monolayers were also processed to assess alterations in tubulin assembly, polymerized tubulin (S2, an index of cytoskeletal integrity), and monomeric tubulin (S1, an index of cytoskeletal disassembly) (polyacrylamide gel electrophoresis fractionation and immunoblotting. In parental cells, oxidant caused: 1) translocation of PKC-lambda from the cytosol to the particulate (membrane + cytoskeletal) fractions, 2) activation of native PKC-lambda, 3) tubulin pool instability (increased monomeric S1 and decreased polymerized S2), 4) disruption of cytoskeletal architecture, and 5) barrier dysfunction (hyperpermeability). In transfected clones, overexpression of the atypical (74 kDa) PKC-lambda isoform by itself ( approximately 3.2-fold increase) led to oxidant-like disruptive effects, including cytoskeletal and barrier hyperpermeability. Overexpressed PKC-lambda was mostly found in particulate cell fractions (with a smaller cytosolic distribution) indicating its activation. Disruption by PKC-lambda overexpression was also potentiated by oxidant challenge. Stable inactivation of endogenous PKC-lambda ( approximately 99.6%) by a dominant-negative protected against all measures of oxidant-induced disruption. We conclude that: 1) oxidant induces disruption of epithelial barrier integrity by disassembling the cytoskeleton, in large part, through the activation of PKC-lambda isoform; and 2) activation of PKC-lambda by itself appears to be sufficient for disruption of cellular cytoskeleton and monolayer barrier permeability. The unique ability to mediate an oxidant-like injury and cytoskeletal depolymerization and instability is a novel mechanism not previously attributed to the atypical subfamily of PKC isoforms.

Blotting, Western↗

PubMed1993

The Xenopus oocyte as an ectopic expression system for the selection of protein isoform-specific antibodies.

A panel of Xenopus oocytes, each injected with cRNA coding for one specific isoform of the rat brain RCK family of voltage gated potassium channel proteins, was employed to screen for isoform-specific monoclonal antibodies. Several days after injection, cryosections of embedded oocytes were produced and were employed in immunohistochemical analysis of antibody binding. Of the advantageous properties of the assay, it employs the native antigen, it can be applied to homooligomeric and heterooligomeric proteins, and cryosections of the same batch can be stored frozen for later tests. The method may be advantageous also for the selection of isoform-specific antibodies of other protein families.

Animals↗

PubMed2000

gamma -glutamyltransferase and its isoform mediate an endoplasmic reticulum stress response.

Although use of multiple alternative first exons generates unique noncoding 5'-ends for gamma-glutamyltransferase (GGT) cDNAs in several species, we show here that alternative splicing events also alter coding exons in mouse GGT to produce at least four protein isoforms. GGTDelta1 introduces CAG four bases upstream of the primary ATG codon and encodes an active GGT heterodimeric ectoenzyme identical to constitutive GGT cDNA but translational efficiency is reduced 2-fold. GGTDelta2-5 deletes the last eight nucleotides of exon 2 through most of exon 5 in-frame, selectively eliminating residues 96-231 from the amphipathic N-terminal subunit, including four N-glycan consensus sites, while leaving the C-terminal hydrophilic subunit intact. GGTDelta7 introduces 22 bases from intron 7 causing a frameshift and a premature stop codon so a truncated polypeptide is encoded terminating with 14 novel residues but retaining the first 339 residues of the native GGT protein. GGTDelta8-9 deletes the terminal four nucleotides of exon 8 plus all of exon 9 and inserts 24 bases from intron 9 in-frame so the C-terminal subunit of the encoded polypeptide loses residues 401-444 but gains eight internal hydrophobic residues. In contrast to the product of GGTDelta1, those derived from GGTDelta2-5, Delta7, Delta8-9 all lack transferase activity and persist as single-chain glycoproteins retained largely in the endoplasmic reticulum as determined by immunofluorescence microscopy and constitutive endoglycosidase H sensitivity in metabolically labeled cells. The developmental-stage plus tissue-specific regulation of the alternative splicing events at GGTDelta7 and GGTDelta8-9 implies unique roles for these GGT protein isoforms. The ability of the GGTDelta1 and GGTDelta7 to mediate the induction of C/EBP homologous protein-10, CHOP-10, and immunoglobulin heavy chain binding protein, BiP, implicates a specific role for these two GGT protein isoforms in the endoplasmic reticulum stress response.

Alternative Splicing↗

PubMed2005

Insulin and human chorionic gonadotropin cause a shift in the balance of sterol regulatory element-binding protein (SREBP) isoforms toward the SREBP-1c isoform in cultures of human granulosa cells.

The isoforms of sterol regulatory element-binding proteins (SREBP) (1a, 1c, and 2) are key transcriptional regulators of lipid biosynthesis. We examined their regulation by gonadotropin and insulin in human granulosa cells. After removal of leukocytes, granulosa cells were exposed to hormonal additions for 16 h starting on d 2 of culture. Progesterone, lactate, and IGF binding protein-1 were measured in culture medium and cellular mRNA measured by competitive RT-PCR. Addition of human chorionic gonadotropin (hCG) (100 ng/ml) stimulated progesterone production (7.0-fold, P < 0.001 vs. control), whereas lactate was increased by hCG (1.6-fold, P < 0.001) and insulin (1.4-fold, P < 0.001; 1000 ng/ml). Insulin decreased IGF binding protein-1 production by 85% (P < 0.001). There were no significant effects on the expression of SREBP-1a but significant increases in mRNA for SREBP-1c with insulin (6.3-fold), hCG (10.4-fold) and in combination (15.2-fold; P < 0.01 for all comparisons). No consistent effects on SREBP-2 were observed. The expression of mRNA for fatty acid synthase, a target gene for SREBP-1c, was increased by hCG (24-fold, P = 0.006) and insulin (19-fold, P = 0.024), which also increased the level of cellular, total fatty acid (1.34-fold; P = 0.03). Thus, hCG and insulin cause a switch toward expression of the SREBP-1c isoform with consequent effects on fatty acid synthesis. We suggest that high circulating insulin, associated with clinically defined insulin resistance, may up-regulate SREBP-1c expression in the ovary.

CCAAT-Enhancer-Binding Proteins↗

PubMed1991

Characterization of isoforms of protein 4.1 present in the nucleus.

Although protein 4.1 was originally identified as an element of the erythrocyte membrane skeleton, its presence in most mammalian cell types is now well described. Antibodies raised against erythrocyte protein 4.1 or synthetic peptides corresponding to the spectrin-actin-binding domain of protein 4.1 react with plasma membranes and, unexpectedly, nuclei of different cell types. Nuclear staining was further confirmed in isolated nuclei prepared from rat liver and human leukaemic cell lines. Immunoblot analysis of subcellular fractions derived from these cells revealed three prominent proteins, of 80, 135 and 145 kDa. The structural relationship of the high-molecular-mass proteins with erythrocyte protein 4.1 was demonstrated by peptide mapping. These results indicate that mammalian nucleated cells contain several isoforms of erythrocyte protein 4.1 and that some high-molecular-mass forms may primarily reside in the nucleus.

Actins↗

PubMed2005

Differential sensitivity of P-Rex1 to isoforms of G protein betagamma dimers.

P-Rex1 is a specific guanine nucleotide exchange factor (GEF) for Rac, which is present in high abundance in brain and hematopoietic cells. P-Rex1 is dually regulated by phosphatidylinositol (3,4,5)-trisphosphate and the Gbetagamma subunits of heterotrimeric G proteins. We examined which of the multiple G protein alpha and betagamma subunits activate P-Rex1-mediated Rac guanine nucleotide exchange using pure, recombinant proteins reconstituted into synthetic lipid vesicles. AlF(-)(4) activated G(s),G(i),G(q),G(12), or G(13) alpha subunits were unable to activate P-Rex1. Gbetagamma dimers containing Gbeta(1-4) complexed with gamma(2) stimulated P-Rex1 activity with EC(50) values ranging from 10 to 20 nm. Gbeta(5)gamma(2) was not able to stimulate P-Rex1 GEF activity. Dimers containing the beta(1) subunit complexed with a panel of different Ggamma subunits varied in their ability to stimulate P-Rex1. The beta(1)gamma(3), beta(1)gamma(7), beta(1)gamma(10), and beta(1)gamma(13HA) dimers all activated P-Rex1 with EC(50) values ranging from 20 to 38 nm. Dimers composed of beta(1)gamma(12) had lower EC(50) values (approximately 112 nm). The farnesylated gamma(11) subunit is highly expressed in hematopoietic cells; surprisingly, dimers containing this subunit (beta(1)gamma(11)) were also less effective at activating P-Rex1. These findings suggest that the composition of the Gbetagamma dimer released by receptor activation may differentially activate P-Rex1.

Animals↗

PubMed2005

Regulation of tau isoform expression and dementia.

In the central nervous system (CNS), aberrant changes in tau mRNA splicing and consequently in protein isoform ratios cause abnormal aggregation of tau and neurodegeneration. Pathological tau causes neuronal loss in Alzheimer's disease (AD) and a diverse group of disorders called the frontotemporal dementias (FTD), which are two of the most common forms of dementia and afflict more than 10% of the elderly population. Autosomal dominant mutations in the tau gene cause frontotemporal dementia with parkinsonism-chromosome 17 type (FTDP-17). Just over half the mutations affect tau protein function and decrease its affinity for microtubules (MTs) or increase self-aggregation. The remaining mutations occur within exon 10 (E10) and intron 10 sequences and alter complex regulation of E10 splicing by multiple mechanisms. FTDP-17 splicing mutations disturb the normally balanced levels of distinct protein isoforms that result in altered biochemical and structural properties of tau. In addition to FTDP-17, altered tau isoform levels are also pathogenically associated with other FTD disorders such as progressive supranuclear palsy (PSP), corticobasal degeneration and Pick's disease; however, the mechanisms remain undefined and mutations in tau have not been detected. FTDP-17 highlights the association between splicing mutations and the pronounced variability in pathology as well as phenotype that is characteristic of inherited disorders.

Alternative Splicing↗

PubMed2003

Relevance of nuclear and cytoplasmic von hippel lindau protein expression for renal carcinoma progression.

Alterations of the von Hippel-Lindau tumor-suppressor gene (VHL) on 3p25-p26 are frequent in clear-cell renal-cell carcinoma (RCC). The VHL protein (pVHL) is implicated in cell-cycle control and gene regulation, and requires transcription-dependent nuclear-cytoplasmic trafficking for its function. There are two biologically active VHL protein isoforms: pVHL(30) and pVHL(19). To study prevalence, subcellular expression and biological significance of pVHL in renal tumors, tissue microarrays with renal-cell carcinomas were immunohistochemically examined for pVHL expression. Antibodies against both protein isoforms (anti-pVHL(30)/pVHL(19)) and against pVHL(30) (anti-pVHL(30); Ig33) were used. The anti-pVHL(30)/pVHL(19) antibody showed nuclear and cytoplasmic pVHL expression, whereas the anti-pVHL(30) antibody (Ig33) detected cytoplasmic pVHL expression, suggesting that the distribution of VHL protein isoforms varies in the nuclear and cytoplasmic compartments of renal tumors. There were 175 of 398 primary clear-cell RCCs (44%) with both nuclear and cytoplasmic pVHL expression. Seventy-seven clear-cell RCCs (19%) showed only nuclear, 22 (6%) showed only cytoplasmic, and 124 tumors (31%) showed no pVHL expression. Notably, combined nuclear and cytoplasmic pVHL expression was associated with low histological grade (P < 0.0001), early tumor stage (P < 0.01), and better prognosis (P < 0.01). These results imply that alteration of subcellular pVHL trafficking is of potential relevance for the biological behavior of clear-cell RCC.

Alleles↗

PubMed2004

Stimulation of the EAAT4 glutamate transporter by SGK protein kinase isoforms and PKB.

The serum and glucocorticoid inducible kinase (SGK) 1 is expressed in brain tissue and upregulated by ischemia, neuronal excitation, and dehydration. The present study has been performed to elucidate the expression of SGK1 in cerebellar Purkinje cells and to explore whether it influences the colocalized glutamate transporter EAAT4. Intense SGK1 staining was observed in Purkinje cells following 48h of water deprivation. The kinase activates glutamate induced current (I(GLU)) in Xenopus oocytes heterologously expressing EAAT4, an effect mimicked by its isoforms SGK2, 3 and PKB. I(GLU) was decreased by the ubiquitin ligase Nedd4-2, an effect partially but not completely reversed by additional coexpression of the SGK kinase isoforms or PKB. According to immunohistochemistry EAAT4 protein abundance in the cell membrane was enhanced by SGK1 and decreased by Nedd4-2. In conclusion, SGK1 expression is upregulated by ischemia, excitation, and dehydration in cerebellar Purkinje cells. The upregulation of SGK1 may serve to stimulate EAAT4 and thus to reduce neuroexcitotoxicity.

Amino Acid Transport System X-AG↗

PubMed1998

Characterization of a calcium-dependent calmodulin-binding domain in the 135-kD human protein 4.1 isoform.

The putative calmodulin binding domain of non-erythroid protein 4.1, previously suggested by Kelly et al. [Kelly, G. M., Zelus, B. D. & Moon, R. T. (1991) J. Biol. Chem. 266, 12469-12473] has been synthesized, and its binding to calmodulin has been studied by fluorescence spectroscopy. For this purpose, the peptide has been N-terminally dansylated. The 4.1 peptide Dns-Abu-S76RGLSRLFSSFLKRPKS92, binds calmodulin in a calcium-dependent way with high affinity (Kd = 23 +/- 6 nM). The peptide inhibits bovine-heart phosphodiesterase with an IC50 of 50 nM. Since the sequence of the peptide shows two putative consensus sites of phosphorylation by cAMP-dependent protein kinase or Ca2+-calmodulin protein-kinase II, the interaction of the two mono-phosphorylated peptides (P4.1 Ser(80-P) and P4.1 Ser(84-P)) and the di-phosphorylated peptide (P4.1 Ser(80-P)/Ser(84-P)) with calmodulin has been investigated. A decrease of affinity by a factor 1.5-8 has been observed for the phosphorylated peptides. CD measurements have shown an increase of the content of alpha helices in the peptides when bound to calmodulin.

Amino Acid Sequence↗

PubMed2005

Regulation of apoptosis by alternative pre-mRNA splicing.

Apoptosis, a phenomenon that allows the regulated destruction and disposal of damaged or unwanted cells, is common to many cellular processes in multicellular organisms. In humans more than 200 proteins are involved in apoptosis, many of which are dysregulated or defective in human diseases including cancer. A large number of apoptotic factors are regulated via alternative splicing, a process that allows for the production of discrete protein isoforms with often distinct functions from a common mRNA precursor. The abundance of apoptosis genes that are alternatively spliced and the often antagonistic roles of the generated protein isoforms strongly imply that alternative splicing is a crucial mechanism for regulating life and death decisions. Importantly, modulation of isoform production of cell death proteins via pharmaceutical manipulation of alternative splicing may open up new therapeutic avenues for the treatment of disease.

Alternative Splicing↗