Calpain modulates cyclin-dependent kinase inhibitor 1B (p27(Kip1)) in cells of the osteoblast lineage

Chopped fibers and nano-hydroxyapatite enhanced silk fibroin porous hybrid scaffolds for bone augmentation

Chopped fiber (CF)- and nano-hydroxyapatite (n-HA)-enhanced silk fibroin (SF) porous hybrid scaffolds (SHCF) were prepared by freeze-drying for bone augmentation. Compared with pristine SF scaffolds, the incorporation of CF and n-HA can significantly enhance the mechanical properties of the composite scaffold. The results of cell experiments and mouse subcutaneous implantation indicated that the SHCF could alleviate foreign body reactions (FBR) led by macrophages and neutrophils, promote the polarization of RAW264.7 cells to anti-inflammatory M2 macrophages, and inhibit the secretion of pro-inflammatory cytokine TNF-α. A rat femoral defect repair model and bulk-RNA-seq analysis indicated that the CF- and n-HA-enhanced SHCF promoted the proliferation and osteogenic differentiation of bone mesenchymal stem cells (BMSCs) by the upregulation of Capns1 expression and regulated the calcium signaling pathway to mediate osteogenesis-related cell behavior, subsequently promoting bone regeneration.

Calpain-calpastatin system and cancer progression

The calpain system is required by many important physiological processes, including the cell cycle, cytoskeleton remodelling, cellular proliferation, migration, cancer cell invasion, metastasis, survival, autophagy, apoptosis and signalling, as well as the pathogenesis of a wide range of disorders, in which it may function to promote tumorigenesis. Calpains are intracellular conserved calcium-activated neutral cysteine proteinases that are involved in mediating cancer progression via catalysing and regulating the proteolysis of their specific substrates, which are important signalling molecules during cancer progression. μ-calpain, m-calpain, and their specific inhibitor calpastatin are the three molecules originally identified as comprising the calpain system and they contain several crucial domains, specific motifs, and functional sites. A large amount of data supports the roles of the calpain-calpastatin system in cancer progression via regulation of cellular adhesion, proliferation, invasion, metastasis, and cellular survival and death, as well as inflammation and angiogenesis during tumorigenesis, implying that the inhibition of calpain activity may be a potential anti-cancer intervention strategy targeting cancer cell survival, invasion and chemotherapy resistance.

Hematopoietic-substrate-1 associated protein X-1 (HAX-1) regulates liver cancer cells growth, metastasis, and angiogenesis through Akt

The aim of this study was to investigate the effects and mechanisms of hematopoietic-substrate-1-associated protein X-1 (HAX-1) on liver cancer cells. Information on HAX-1 from liver cancer patients was analyzed by the Cancer Genome Atlas (TCGA) program. Cell migration and invasion abilities were respectively tested by scratch assay and transwell assay. Tube formation assay was applied to detect angiogenesis protein and mRNA was determined using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. We found that the median month survival of HAX-1 overexpressing liver cancer patients was shorter than that of HAX-1 normal liver cancer patients. HAX-1 was overexpressed in liver cancer tissues and cells, and HAX-1 overexpression promoted the liver cancer cells growth, migration, and invasion, whereas silencing HAX-1 produced the opposite results. Inhibition of Akt by LY294002 reversed the migration and invasion abilities of liver cancer cells, and inhibited the ability of cells growth and angiogenesis. Silencing PIK3CA enhanced the inhibitory effects of HAX-1 silencing on the viability, migration, and invasion of liver cancer cells. HAX-1 affected liver cancer cells metastasis and angiogenesis by affecting Akt phosphorylation and FOXO3A expression.

Differential Proteomic Analysis Reveals Protein Networks and Pathways that May Contribute to Helicobacter pylori FKBP-Type PPIase-Associated Gastric Diseases

PURPOSE

Though Helicobacter pylori (H. pylori) has been classified as class I carcinogen, key virulence factor generated by H. pylori that causes gastric cancer remains to be fully determined. Recently, we identified a gastric cancer-associated H. pylori gene, peptidylprolyl isomerase-FK506 binding protein (PPIase-FKBP), and showed that PPIase-FKBP was capable of inducing oncogenic transformation of gastric epithelial cells. But its mechanism was unclear.

EXPERIMENTAL DESIGN

We carried out a comparative proteomic analysis of human gastric epithelial cells that either express PPIase-FKBP or green fluorescent protein using 2-DE and then MALDI-TOF-MS/MS.

RESULTS

Our results identified 28 differentially expressed proteins induced by PPIase-FKBP. These proteins participate in some cellular biological processes, such as cell proliferation, cell apoptosis and DNA replication, mRNA splicing, and protein biosynthesis. Ingenuity Pathway Analysis categorized the 28 proteins into two molecular interaction networks, involved primarily in cancer and gastrointestinal diseases.

CONCLUSIONS AND CLINICAL RELEVANCE

Our results provided insight on the protein interaction networks and signaling pathways that may contribute to PPIase-FKBP-associated gastric diseases and may lead to a better understanding of the mechanisms indicating the oncogenic effects of H. pylori PPIase-FKBP.

Overview of calpain-mediated regulation of bone and fat mass in osteoblasts

The receptor for parathyroid hormone (PTH) and PTH-related peptide (PTH1R) belongs to the class II G protein-coupled receptor superfamily. The calpain small subunit encoded by the gene Capns1 is the second protein and the first enzyme identified by a yeast two-hybrid screen using the intracellular C-terminal tail of the rat PTH1R. The calpain regulatory small subunit forms a heterodimer with the calpain large catalytic subunit and modulates various cellular functions as a cysteine protease. To investigate a physiological role of the calpain small subunit in cells of the osteoblast lineage, we generated osteoblast-specific Capns1 knockout mouse models and characterized their bone phenotype. Molecular mechanisms by which calpain modulates cell proliferation of the osteoblast lineage were further examined in vitro. Moreover, we utilized the mutant mice as a disease model of osteoporosis accompanied with impaired bone resorptive function and suggested a possible clinical translation of our basic research finding.

Purified vitexin compound 1 inhibits growth and angiogenesis through activation of FOXO3a by inactivation of Akt in hepatocellular carcinoma

Vitexins, isolated from the seeds of the Chinese herb Vitex negundo, is known to exert antitumor activity in cancer xenograft models and cell lines. The aim of the current study was to examine whether the Akt/forkhead box protein O3a (FOXO3a) pathway mediates the biological effects of purified vitexin compound 1 (VB-1) in hepatocellular carcinoma (HCC) cells. The effect of VB-1 on the viability of the HCC cell lines HepG2, Hep3B, Huh-7 and the human embryonic liver cells L-02 was investigated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Growth inhibition was assessed by clonogenic assay, and cell cycle arrest was investigated using flow cytometry. Inhibition of angiogenesis was evaluated using a matrigel in vitro HUVEC tube formation assay. The effects on the Akt/FOXO3a pathway were detected by western blotting. VB-1 suppressed the proliferation of HepG2, Hep3B, Huh-7 cells, but had little effect on L-02 cells. VB-1 inhibited anchorage-dependent and -independent HepG2 cell growth in a concentration-dependent manner by induction of cell cycle arrest at G1/G0. VB-1 also reduced the secretion of vascular endothelial growth factor (VEGF), resulting in the inhibition of endothelial tube formation. Phosphorylated Akt and its downstream effector FOXO3a were downregulated in VB-1-treated HepG2 cells. Knockdown of Akt1 by small interfering RNA (siRNA) enhanced growth inhibition, and silencing FOXO3a by siRNA attenuated this action. VB-1 inhibited growth and induced cell cycle arrest at G1/G0 by regulating the Akt/FOXO3a pathway. The findings suggested that VB-1 is a potentially promising candidate for the treatment of HCC.

Distinct regulatory functions of calpain 1 and 2 during neural stem cell self-renewal and differentiation

Calpains are calcium regulated cysteine proteases that have been described in a wide range of cellular processes, including apoptosis, migration and cell cycle regulation. In addition, calpains have been implicated in differentiation, but their impact on neural differentiation requires further investigation. Here, we addressed the role of calpain 1 and calpain 2 in neural stem cell (NSC) self-renewal and differentiation. We found that calpain inhibition using either the chemical inhibitor calpeptin or the endogenous calpain inhibitor calpastatin favored differentiation of NSCs. This effect was associated with significant changes in cell cycle-related proteins and may be regulated by calcium. Interestingly, calpain 1 and calpain 2 were found to play distinct roles in NSC fate decision. Calpain 1 expression levels were higher in self-renewing NSC and decreased with differentiation, while calpain 2 increased throughout differentiation. In addition, calpain 1 silencing resulted in increased levels of both neuronal and glial markers, β-III Tubulin and glial fibrillary acidic protein (GFAP). Calpain 2 silencing elicited decreased levels of GFAP. These results support a role for calpain 1 in repressing differentiation, thus maintaining a proliferative NSC pool, and suggest that calpain 2 is involved in glial differentiation.