The therapeutic use of ionizing radiation (e.g., X-rays and γ-rays) needs to inflict minimal damage on non-target tissue. Recent studies have shown that substance P (SP) mediates multiple activities in various cell types, including cell proliferation, anti-apoptotic responses, and inflammatory processes. The present study investigated the effects of SP on γ-irradiated bone marrow stem cells (BMSCs). In mouse bone marrow extracts, SP prolonged activation of Erk1/2 and enhanced Bcl-2 expression, but attenuated the activation of apoptotic molecules (e.g., p38 and cleaved caspase-3) and down-regulated Bax. We also observed that SP-decreased apoptotic cell death and stimulated cell proliferation in γ-irradiated mouse bone marrow tissues through TUNEL assay and PCNA analysis. To determine how SP affects bone marrow stem cell populations, mouse bone marrow cells were isolated and colony-forming unit (CFU) of mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) was estimated. SP-pretreated ones showed higher CFUs of MSC and HSC than untreated ones. Furthermore, when SP was pretreated in cultured human MSC, it significantly decreased apoptotic cells at 48 and 72 h after γ-irradiation. Compared with untreated cells, SP-treated human MSCs showed reduced cleavage of apoptotic molecules such as caspase-8, -9, -3, and poly ADP-ribose polymerase (PARP). Thus, our results suggest that SP alleviates γ-radiation-induced damage to mouse BMSCs and human MSCs via regulation of the apoptotic pathway.

Several groups have reported that TGFb1 regulates cellular responses to g-irradiation; however, the exact mechanism has not been fully elucidated. In the current study, the role of TGFb1 in cellular responses to g-irradiation was investigated in detail. The data indicate that TGFb1 pretreatment decreased the aftermath of ionizing radiation (IR)-induced DNA damage in a SMAD-dependent manner. To determine the underlying mechanism for these effects, the extent of IR-induced DNA repair activity in the presence or absence of TGFb1 was examined. Studies reveal that TGFb1 upregulated DNA ligase IV (Lig4), augmented IR-induced nuclear retention of the DNA ligase, and enhanced nonhomologous end-joining (NHEJ) repair activity. In addition, knockdown of Lig4 reduced the TGFb1-induced protection against IR. Overall, these data indicate that TGFb1 facilitates the NHEJ repair process upon g-irradiation and thereby enhances long-term survival.Implications: These findings provide new insight and a possible approach to controlling genotoxic stress by the TGFb signaling pathway. Mol Cancer Res; 13(2); 319-29. Ó2014 AACR.

Insulin secretory granules (SGs) mediate the regulated secretion of insulin, which is essential for glucose homeostasis. The basic machinery responsible for this regulated exocytosis consists of specific proteins present both at the plasma membrane and on insulin SGs. The protein composition of insulin SGs thus dictates their release properties, yet the mechanisms controlling insulin SG formation, which determine this molecular composition, remain poorly understood. VPS41, a component of the endolysosomal tethering homotypic fusion and vacuole protein sorting (HOPS) complex, was recently identified as a cytosolic factor involved in the formation of neuroendocrine and neuronal granules. We now find that VPS41 is required for insulin SG biogenesis and regulated insulin secretion. Loss of VPS41 in pancreatic β-cells leads to a reduction in insulin SG number, changes in their transmembrane protein composition, and defects in granule-regulated exocytosis. Exploring a human point mutation, identified in patients with neurological but no endocrine defects, we show that the effect on SG formation is independent of HOPS complex formation. Finally, we report that mice with a deletion of VPS41 specifically in β-cells develop diabetes due to severe depletion of insulin SG content and a defect in insulin secretion. In sum, our data demonstrate that VPS41 contributes to glucose homeostasis and metabolism.

No abstract

No abstract

Heat shock protein 90 (HSP90) regulates the stability of various proteins and plays an essential role in cellular homeostasis. Many client proteins of HSP90 are involved in cell growth, survival, and migration; processes that are generally accepted as participants in tumorigenesis. HSP90 is also up-regulated in certain tumors. Indeed, the inhibition of HSP90 is known to be effective in cancer treatment. Recently, studies showed that HSP90 regulates transforming growth factor β1 (TGF-β1)-induced transcription by increasing the stability of the TGF-β receptor. TGF-β signaling also has been implicated in cancer, suggesting the possibility that TGF-β1 and HSP90 function cooperatively during the cancer cell progression. Here in this paper, we investigated the role of HSP90 in TGF-β1-stimulated Mv1Lu cells. Treatment of Mv1Lu cells with the HSP90 inhibitor, 17-allylamino-demethoxy-geldanamycin (17AAG), or transfection with truncated HSP90 (ΔHSP90) significantly reduced TGF-β1-induced cell migration. Pretreatment with 17AAG or transfection with ΔHSP90 also reduced the levels of phosphorylated Smad2 and Smad3. In addition, the HSP90 inhibition interfered the nuclear localization of Smads induced by constitutively active Smad2 (S2EE) or Smad3 (S3EE). We also found that the HSP90 inhibition decreased the protein level of importin-β1 which is known to regulate R-Smad nuclear translocation. These data clearly demonstrate a novel function of HSP90; HSP90 modulates TGF-β signaling by regulating Smads localization. Overall, our data could provide a detailed mechanism linking HSP90 and TGF-β signaling. The extension of our understanding of HSP90 would offer a better strategy for treating cancer.

No abstract

Insulin secretory granules (SGs) mediate the regulated secretion of insulin, which is essential for glucose homeostasis. The basic machinery responsible for this regulated exocytosis consists of specific proteins present both at the plasma membrane and on insulin SGs. The protein composition of insulin SGs thus dictates their release properties, yet the mechanisms controlling insulin SG formation, which determines this molecular composition, remain poorly understood.VPS41, a component of the endo-lysosomal tethering HOPS complex, was recently identified as a cytosolic factor involved in the formation of neuroendocrine and neuronal granules. We now find that VPS41 is required for insulin SG biogenesis and regulated insulin secretion. Loss of VPS41 in pancreatic b-cells leads to a reduction in insulin SG number, changes in their transmembrane protein composition, and defects in granule regulated exocytosis. Exploring a human point mutation, identified in patients with neurological but no endocrine defects, we show that the effect on SG formation is independent of HOPS complex formation. Finally, we report that mice with a deletion of VPS41 specifically in β-cells develop diabetes due to severe depletion of insulin SG content and a defect in insulin secretion. In sum, our data demonstrate that VPS41 contributes to glucose homeostasis and metabolism. * *