Insulin-like growth factor binding proteins initiate cell death and extracellular matrix remodeling in the mammary gland

We have demonstrated that insulin-like growth factor binding protein-5 (IGFBP-5) production by mammary epithelial cells increases dramatically during forced involution of the mammary gland in rats, mice and pigs. We proposed that growth hormone (GH) increases the survival factor IGF-I, whilst prolactin (PRL) enhances the effects of GH by decreasing the concentration of IGFBP-5, which would otherwise inhibit the actions of IGFs. To demonstrate a causal relationship between IGFBP-5 and cell death, we created transgenic mice expressing IGFBP-5, specifically, in the mammary gland. DNA content in the mammary glands of transgenic mice was decreased as early as day 10 of pregnancy. Mammary cell number and milk synthesis were both decreased by approximately 50% during the first 10 days of lactation. The concentrations of the pro-apoptotic molecule caspase-3 was increased in transgenic animals whilst the concentrations of two pro-survival molecules Bcl-2 and Bcl-x were both decreased. In order to examine whether IGFBP-5 acts by inhibiting the survival effect of IGF-I, we examined IGF receptor- and Akt-phoshorylation and showed that both were inhibited. These studies also indicated that the effects of IGFBP-5 could be mediated in part by IGF-independent effects involving potential interactions with components of the extracellular matrix involved in tissue remodeling, such as components of the plasminogen system, and the matrix metallo-proteinases (MMPs). Mammary development was normalised in transgenic mice by R3-IGF-I, an analogue of IGF-I which binds weakly to IGFBPs, although milk production was only partially restored. In contrast, treatment with prolactin was able to inhibit early involutionary processes in normal mice but was unable to prevent this in mice over-expressing IGFBP-5, although it was able to inhibit activation of MMPs. Thus, IGFBP-5 can simultaneously inhibit IGF action and activate the plasminogen system thereby coordinating cell death and tissue remodeling processes. The ability to separate these properties, using mutant IGFBPs, is currently under investigatio

Academic Achievement and the Ability of Post-Secondary Students to Read Assigned Materials

This study provides a rationale for adopting course materials. It demonstrates the relationship between ability to read assigned materials and academic achievement, and that selection of materials creates two groups having different probabilities of success. The sample was selected from a population of all students enrolled in Principles of Economics courses at North Texas State University in the spring semester of 1986. The Nelson-Denny Reading Test was used to determine reading ability. Assigned materials were analyzed for readability. A frustration level was determined and used to divide the sample: the group of interest, those with reading abilities below the frustration level who underwent the treatment of reading materials written above their ability to comprehend; and the comparison group, those with reading abilities above the frustration level who did not undergo the treatment

Asymmetric paternal effect on offspring size linked to parent-of-origin expression of an insulin-like growth factor

Research was supported by PAPIIT grant IN216111 (CMG), CONACyT PhD scholarship 351769 (YSL), and the Howard Hughes International Research Program (JPVC).Sexual reproduction brings together reproductive partners whose long-term interests often differ, raising the possibility of conflict over their reproductive investment. Males that enhance maternal investment in their offspring gain fitness benefits, even if this compromises future reproductive investment by iteroparous females. When the conflict occurs at a genomic level, it may be uncovered by crossing divergent populations, as a mismatch in the coevolved patterns of paternal manipulation and maternal resistance may generate asymmetric embryonic growth. We report such an asymmetry in reciprocal crosses between populations of the fish Girardinichthys multiradiatus. We also show that a fragment of a gene which can influence embryonic growth (Insulin-Like Growth Factor 2; igf2) exhibits a parent-of-origin methylation pattern, where the maternally inherited igf2 allele has much more 5′ cytosine methylation than the paternally inherited allele. Our findings suggest that male manipulation of maternal investment may have evolved in fish, while the parent-of-origin methylation pattern appears to be a potential candidate mechanism modulating this antagonistic coevolution process. However, disruption of other coadaptive processes cannot be ruled out, as these can lead to similar effects as conflict.Publisher PDFPeer reviewe

Insulin-like Growth Factor Binding Protein Expression in SH-SY5Y Neuroblastoma Cells

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75524/1/j.1749-6632.1993.tb26228.x.pd

The insulin-like growth factors

"The insulin-like growth factors (IGF-I and IGF-II) are single-chain polypeptides with structural homology to proinsulin. They regulate proliferation and differentiation of a multitude of cell types and are capable of exerting insulin-like metabolic effects. Unlike insulin, they are produced by most tissues of the body and are abundant in the circulation. Thus the IGFs have the potential to act via endocrine as well as autocrine andlor paracrine mechanisms. The IGFs exert their effects at the cellular level by interacting with the Type-I IGF receptor (IGF-I receptor). They also bind to the Type II1mannose- 6-phosphate receptor (IGF-II receptor) and insulin receptors, as well as high affinity binding proteins (IGFBPs). Like the IGFs, the IGFBPs are produced by multiple cell types and have been shown to modulate IGF bioactivity. The recent availability of cDNA probes and antibodies for the IGFs, IGF receptors, and IGFBPs has led to a substantial increase in published studies of IGF physiology. This review attempts to integrate recent information regarding coordinate regulation and function of the IGFs, their receptors, and IGFBPs.

Inhibition of the Unfolded Protein Response by Ricin A-Chain Enhances Its Cytotoxicity in Mammalian Cells

Ricin is a highly toxic type II ribosome-inactivating protein that has potential as a biochemical weapon and as the toxic component of immunotoxins. The unfolded protein response (UPR) is a survival response that helps cells to recover from endoplasmic reticulum (ER) stress. Failure to recover from ER stress leads to apoptosis. In yeast, ricin-A-chain (RTA), the enzymatic component of ricin, inhibits UPR. Our goals were to determine if RTA inhibits UPR in two epithelial cell lines and if this affects RTA cytotoxicity. RTA alone did not induce UPR. However, RTA inhibited both phosphorylation of inositol-requiring enzyme 1 (IRE1) and splicing of X-box binding protein1 mRNA by the UPR-inducing agent tunicamycin (Tm). The ability of dithiothreitol (DTT) to activate eukaryotic translation initiation factor 2 alpha (eIF2α), a component of the PERK pathway, was also inhibited by RTA. Treatment with RTA in combination with Tm or DTT inhibited protein synthesis more than either agent did alone in one cell line, while caspase cleavage was enhanced by the treatment combination in both cell lines. These data indicate that RTA is more cytotoxic when UPR is inhibited. This ability to inhibit UPR may enhance the potential of RTA as a therapeutic immunotoxin in solid tumors

Regulation of insulin-like growth factor binding protein synthesis and secretion in human retinal pigment epithelial cells

Cultured human retinal pigment epithelial cells (RPE) secrete insulin-like growth factor binding proteins (IGFBPs), a family of polypeptides which modulate the actions of the insulin-like growth factors. RPE cells secrete two IGFBPs with Mr estimates of 34,000 and 46,000, respectively. Treatment of RPE cells with IGF-I markedly stimulated the secretion of the 46,000 Mr form. This stimulation occurred via an IGF-I receptor independent mechanism because both [QAYL]IGF-I (an IGF-I analogue with decreased affinity for the IGFBPs but normal affinity for the IGF-I receptor) and Α-IR 3 (a blocking monoclonal antibody against the IGF-I receptor) had no effect on IGF-I stimulated increases in IGFBPs. Additionally, [QAYL]IGF-I enhanced RPE cell proliferation to the same magnitude as IGF-I. Treatment with IGF-I, [QAYL]IGF-I, or Α-IR 3 had no effect on steady-state levels of the 2.5 kb IGFBP-3 or the 1.3 kb IGFBP-6 mRNA transcripts as measured by Northern blotting and quantitative autoradiography. Forskolin and a group of candidate growth factors, including platelet-derived growth factor, epidermal growth factor, and acidic and basic fibroblast growth factor, modestly increased IGFBP secretion when compared to untreated cells, but these effects were small when compared to IGF-I treatment. Fetal calf serum enhanced the presence of the 2.5 kb IGFBP-3 mRNA transcript in a dose-dependent fashion but had no effect on the 1.3 kb IGFBP-6 mRNA transcript. IGF-I, forskolin, and the candidate growth factors had no effect on either IGFBP-3 or IGFBP-6 mRNA. These data suggest that the production of IGFBPs in human RPE cells is regulated by distinct mechanisms which include (1) an IGF-I receptor independent interaction of IGF-I with secreted IGFBPs and (2) de novo synthesis of IGFBPs by serum-containing factors. © 1994 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49887/1/1041580124_ftp.pd