Roles for insulin and ecdysteroids in differentiation of an insect cell line of epidermal origin

Abstract

During postembryonic development of insects, molting cycles affect epidermal cells with alternate periods of proliferation and differentiation. Cells of the cell line established from imaginal discs of the Indian meal moth (IAL-PID2) differentiate under the action of the molting hormone, 20-hydroxyecdysone, in a manner that is meaningful in terms of the development of the tissue from which they were derived. In particular, the hormone caused an accumulation of the cells in the G2 phase of their cycle and induced the formation of epithelial-like aggregates and the synthesis of specific proteoglycans. Recent discovery of members of the insulin superfamily in insects and the role of growth factors played by this family of molecules in vertebrates led us to check for their potential effects on IAL-PID2 cell cycle regulation. On the one hand, our results showed that insulin was involved in partial resumption of the cell cycle after an arrest caused by serum deprivation, but that other growth factors present in fetal calf serum were needed for full completion of mitosis. On the other hand, the cytostatic effect of 20-hydroxyecdysone was reversible, and, prior exposure of the cells to the hormone allowed the cells to complete one cell cycle in serum-free medium. These results suggest that the production of autocrine growth factors induced by ecdysteroids could circumvent the absence of serum. This cell culture model provides potential for further study of interactions between ecdysteroids and growth factor homologs during differentiation of insect epidermal cells.

The SIN3/RPD3 Deacetylase Complex Is Essential for G2 Phase Cell Cycle Progression and Regulation of SMRTER Corepressor Levels

“…In accord with published observations, we found that treatment of S2 cells with ecdysone caused a rapid and severe G 2 /M phase cell cycle block (Fig. 7C) (4,8,11,19,53). Thus, the SIN3/RPD3 complex, SMRTER, and EcR are required at similar points in the cell cycle.…”

“…These observations highlight the importance of the balance of histone acetylationdeacetylation during the cell cycle. The SIN3/RPD3 deacetylase complex may participate in regulation of G 2 cell cycle progression, as ecdysone treatment of Drosophila tissue culture cells causes arrest in the G 2 phase of the cell cycle (4,9,11,19).…”

Peptides that elicit midgut stem cell differentiation isolated from chymotryptic digests of hemolymph from Lymantria dispar pupae

“…A comparison of the sequences of the synthetic peptides is presented in Figure 8. Unlike MDF1 and 2, MDF3 and 4 were not homologous to other peptides or proteins in the Swissprot database (BLAST) (Altschul et al, 1997), or to known insect growth factors or cytokines (Ebberink et al, 1989;Hatt et al, 1994;Ferkovich et al, 1995;Homma et al, 1996;Strand et al, 2000). All of the natural and synthetic MDF peptides induced dosedependent differentiation of H. virescens midgut stem cells to mature goblet and columnar cells in vitro, and induced similar effects when introduced alone at the same concentrations in this work.…”

Effect of bombyxin-II, an insulin-related peptide of insects, on Bombyx mori hemocyte division in single-cell culture

“…The growth-promoting activity of insulin and insulin-like growth factors has been amply documented in both vertebrate cells and organ cultures. In insect cell cultures, exogenous insulin and insulin-like growth factors provoke physiological effects (Seecof and Dewhurst, 1974;Davis and Shearn, 1977;Martin and Shearn, 1980;Mosna, 1981;Wyss, 1982;Cullen and Milner, 1991;Hatt et al, 1994Hatt et al, , 1997 and mammalian insulin is presently a routine additive to Drosophila culture media (Wyss, 1988;Echalier, 1997). Nijhout and Grunert (2002) reported that bombyxin-II stimulates cell division and growth of wing imaginal disks of Precis coenia.…”