Pcif1 modulates Pdx1 protein stability and pancreatic β cell function and survival in mice

Claiborn, Kathryn; Sachdeva, Mira M.; Cannon, Corey E.; Groff, David; Singer, Jeffrey D.; Stoffers, Doris A.

doi:10.1172/jci40440

Cited by 79 publications

(76 citation statements)

References 43 publications

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“…S1B). Homozygous mutant pups of both strains died shortly after birth, similar to a previous report, consistent with the prediction that they are both likely null (25) (Fig. S1 C and D and Tables S1-S3).…”

Section: Resultssupporting

confidence: 90%

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Spop promotes skeletal development and homeostasis by positively regulating Ihh signaling

Cai

Liu

2016

Proc. Natl. Acad. Sci. U.S.A.

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Indian Hedgehog (Ihh) regulates chondrocyte and osteoblast differentiation through the Glioma-associated oncogene homolog (Gli) transcription factors. Previous in vitro studies suggested that Speckletype POZ protein (Spop), part of the Cullin-3 (Cul3) ubiquitin ligase complex, targets Gli2 and Gli3 for degradation and negatively regulates Hedgehog (Hh) signaling. In this study, we found defects in chondrocyte and osteoblast differentiation in Spop-null mutant mice. Strikingly, both the full-length and repressor forms of Gli3, but not Gli2, were up-regulated in Spop mutants, and Ihh target genes Patched 1 (Ptch1) and parathyroid hormone-like peptide (Pthlh) were down-regulated, indicating compromised Hh signaling. Consistent with this finding, reducing Gli3 dosage greatly rescued the Spop mutant skeletal defects. We further show that Spop directly targets the Gli3 repressor for ubiquitination and degradation. Finally, we demonstrate in a conditional mutant that loss of Spop results in brachydactyly and osteopenia, which can be rescued by reducing the dosage of Gli3. In summary, Spop is an important positive regulator of Ihh signaling and skeletal development.T he human skeleton provides essential mechanical support, mobility, and mineral storage critical for health (1). In development, most bones form through endochondral ossification in which chondrocytes in the growth plate proliferate, undergo hypertrophic differentiation, and secrete calcium-containing extracellular matrix (2). The osteoblasts in the perichondrium, a thin layer of tissue surrounding the cartilage, replace the dying chondrocytes and secrete more bone matrix. On the other hand, osteoclasts, derived from white blood cells, invade and digest bone matrix. The balance between the osteoblast and osteoclast activities allows calcium homeostatic control and bone health. In osteopenia and osteoporosis, conditions afflicting more than 10 million Americans, an abnormal decrease in osteoblast activity or increase in osteoclast activity results in the loss of bone mass (1, 3). Unfortunately, our understanding of these bone diseases has been hindered by incomplete knowledge in the molecular mechanisms underlying endochondral bone development and remodeling.Indian Hedgehog (Ihh), a member of the Hedgehog (Hh) family of signaling proteins, is essential for endochondral bone development (4). Ihh regulates gene expression through the Gli family of transcription factors, which act as both transcriptional activators and repressors (5). In the absence of Hh, efficient proteolytic processing turns Gli3 into a transcriptional repressor (Gli3R) whereas processing of Gli2 is rather inefficient (6-8). Hh inhibits Gli processing and converts the full-length Gli proteins into transcriptional activators. Both Gli2 and Gli3 play important roles in the regulation of bone formation downstream of Ihh (9-12).Ihh maintains the expression of parathyroid hormone-like peptide (Pthlh) (Mouse Genome Informatics) in the periarticular perichondrium (13), which then stimulates the prol...

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Section: Resultssupporting

confidence: 90%

“…Overexpression of Spop in Xenopus similarly reduces Hh pathway activation (24). An Spop mutant mouse strain was analyzed previously, but defects only in endocrine pancreas were reported (25). Another Speckle-type POZ protein, Spop-like (Spopl), exhibits similar substrate specificity and similar, albeit somewhat weaker, ubiquitination activity as Spop (26).…”

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confidence: 99%

Spop promotes skeletal development and homeostasis by positively regulating Ihh signaling

Cai

Liu

2016

Proc. Natl. Acad. Sci. U.S.A.

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“…In humans, the roles for SPOP in regulating the Hh and TNF pathways have been conserved (21,22), and several other SPOP substrates have been identified as well, including the death domain-associated protein (Daxx) (5), the polycomb group protein BMI-1, the phosphatidylinosital phosphate kinase PIPKIIβ (23), the transcription factor Gli (24), the Jun-kinase phosphatase Puckered (14) and Pdx1 (25), and the histone variant MacroH2A (4). Together, these previous results indicate that SPOP plays important roles during cell apoptosis, proliferation, and animal development.…”

Section: Discussionmentioning

confidence: 99%

Decreased expression of the SPOP gene is associated with poor prognosis in glioma

Ding

Song

et al. 2014

International Journal of Oncology

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Abstract. This study suggests that speckle-type POZ protein (SPOP) may be a tumor suppressor gene and its prognostic value in human glioma. Real-time quantitative RT-PCR (qRT-PCR), western blotting, and immunohistochemical staining were used to examine SPOP expression in glioma tissues and normal brain (NB) tissues. The relationships between the SPOP expression levels, the clinicopathological factors, and patient survival were investigated. The molecular mechanisms of SPOP expression and its effects on cell viability, migration and invasion were also explored by MTT assay, wound-healing assays and Transwell assay. SPOP mRNA and protein levels were downregulated in glioma tissues compared to NB. Immunohistochemical staining results showed low expression in 62.2% (61/98) of glioma samples, while high expression in 75% (9/12) of NB samples, and the difference was statistically significant (P=0.014). In addition, decreased SPOP was associated disease progression in glioma samples, the expression level of SPOP was positively correlated with mean tumor diameter (MTD) (P= 0.021) and the status of tumor grade and histological type (WHO I, II, III and IV) (P= 0.032) in glioma patients. Additionally, the overall survival of patients with low SPOP expression was significantly worse than that of SPOP-high patients (P= 0.001). In vitro overexpression of SPOP markedly inhibited cell viability, migration and invasion in vitro. These findings suggest that SPOP has potential use as novel biomarker of glioma and may serve as an independent predictive factor for prognosis of glioma patients.

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“…Cullin family members accompanied by their partners in cullin-RING E3 ligase complexes (CRLs) play important roles in neuron activity, in cardiovascular function, and in the development of the reproductive system and pancreatic islets (14,22). In particular, cullin 4B (CUL4B) mutations cause mental retardation, short stature, and obesity (23,24).…”

Section: Introductionmentioning

confidence: 99%

A cullin 4B-RING E3 ligase complex fine-tunes pancreatic δ cell paracrine interactions

Cui

Yang

et al. 2017

Journal of Clinical Investigation

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Figure 1. CUL4B deficiency in pancreatic δ cells impairs glucose metabolism. (A and B)Western blots and quantitative data for CUL4A and CUL4B protein levels in islets from 12-week-old diabetic db/db mice and their heterozygous littermates (db/+). n = 6 mice per group. Representative Western blots from at least 3 independent experiments are shown. (C) Immunostaining for CUL4B (green) and somatostatin (SST, red) in pancreatic sections from db/db and db/+ mice. Scale bar: 100 μm. n = 6 mice per group; 4-7 random areas were selected from each islet section, and 10 sections were randomly selected from each mouse. Insulininduced decreases in blood glucose levels were significantly lower in Sst-Cre +/-Cul4b fl/Y mice than in their WT littermates, and they did not return to baseline levels at the 2-hour time point, whereas the levels of their WT littermates did (n = 9-11). *P < 0.05; **P < 0.01; ***P < 0.001. db/db mice were compared with their db/+ littermates, and Sst-Cre +/-Cul4b fl/Y mice were compared with their WT littermates. Error bars in F represent mean ± SD; other bars represent mean ± SEM. All data were analyzed using 1-way ANOVA. The Journal of Clinical Investigation R E S E A R C H A R T I C L E2 6 3 3 jci.orgVolume 127 Number 7 July 2017mental Figure 1E). Immunofluorescence also showed no significant differences in islet or β or δ cell numbers between +/-mice, the knockout mice exhibited increased glucose levels after 2 hours of feeding following a 16-hour fast ( Figure 1G). Accordingly, during a glucose tolerance test, the blood glucose levels of Sst-Cre +/-Cul4b fl/Y mice were 33% and 30% higher at 30 minutes and 120 minutes, respectively, than those of the control group consisting of both Sst-Cre +/-and Cul4b fl/Y mice ( Figure 1H). In addition, during the insulin tolerance test, the blood glucose levels of Sst-Cre +/-Cul4b fl/Y mice unexpectedly decreased more dramatically and rapidly than those of the Sst-Cre +/-control mice in response to insulin stimulation ( Figure 1I). Insulin and somatostatin content as well as kidney, brain, heart, liver, and stomach weights were not found to be significantly different between the mice was 140% and 40% higher than that of Sst-Cre +/-mice at 5 minutes and 60 minutes, respectively ( Figure 2H). In contrast to the results found for the Sst-Cre +/-Cul4b fl/Y mice, CUL4B defistrated that CRL4 ubiquitinates WD repeat-containing protein 5 (WDR5), a core subunit of H3K4 methyltransferase complexes, for degradation in the nucleus, thereby promoting increased H3K4 methylation levels (30). However, whether CUL4B or its E3 ligase complex CRL4B-PRC2 participates in the functioning or development of Langerhans islets has not been studied. In this study, we found that CUL4B expression levels are decreased in db/db mice. Therefore, we crossed mice expressing Cre under the insulin II promotor (Ins2-Cre) and mice expressing Cre under the somatostatin promoter (Sst-Cre) with Cul4b fl/fl mice to characterize CUL4B functions in specific cell types of the islet circuit. Although In...

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Pcif1 modulates Pdx1 protein stability and pancreatic β cell function and survival in mice

Cited by 79 publications

References 43 publications

Spop promotes skeletal development and homeostasis by positively regulating Ihh signaling

Spop promotes skeletal development and homeostasis by positively regulating Ihh signaling

Decreased expression of the SPOP gene is associated with poor prognosis in glioma

A cullin 4B-RING E3 ligase complex fine-tunes pancreatic δ cell paracrine interactions

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