COCKROACH MIDGUT PEPTIDES THAT REGULATE CELL PROLIFERATION, DIFFERENTIATION AND DEATH IN VITRO

Authors: SAKAI, TAKUDA - KOBE UNIVERSITY JAPAN; TAKEDA, MAKIO - KOBE UNIVERSITY JAPAN; LOEB, MARCIA

Submitted to: In Vitro Cellular And Developmental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Vertebrate cells are regulated by an array of cytokines; they control cell division, secretion of products, cell movement, differentiation, and cell death, among other things. Most of the vertebrate cytokines are chemically identified peptides. However, vertebrate peptides generally do not affect affect insect cells. We have been attempting to identify the insect growth factors that control the insect midgut. The midgut is the largest organ in the feeding caterpillar, and is essential for digesting and processing the food that the caterpillar eats. Heliothis virescens is a most aggressive caterpillar that eats thousands of dollars worth of crops per year, and is becoming increasingly resistant to insecticides. If a compound native to these insects could be found that prevented or inhibited food digestion and lead to the death of the insects by starvation, a great contribution to pest prevention could be made. When cockroaches are starved, their guts naturally shrink in size as cells are lost. In this work, we tested peptides isolated from the midguts of starved cockroaches in our cultured midgut cells. Some of the peptides did indeed cause a 50 - 80% reduction in the number of mature cultured cells, indicating that the peptides can work in caterpillar cells as well as roach gut. We are now engaged in characterizing these peptides. When we fully determine structure and stability, we hope to be able to use them as Lepidopteran pest control agents. This work will be of use to scientists only at this stage.

Technical Abstract: The number of insect midgut cells is maintained homeostatically in vivo and in vitro. However, during starvation the midgut shrinks and the rate of cell replacement appears to be supressed. When they undergo metamorphosis, the internal organs of insects are drastically remodeled by cell proliferation, differentiation and apoptotic processes, and the net number of cells usually increases. An extract of 1650 midguts of Periplaneta americana was fractionated by HPLC to obtain peptides that regulate these processes. The HPLC fractions were tested for myotropic activity in the foregut and for effects on cell proliferation or loss in cultures of larval Heliothis virescens midgut cells and a cell line derived from last-instar larval fat body of Mamestra brassicae. Some fractions stimulated midgut stem cell proliferation and differentiation, while others caused loss of differentiated columnar and goblet cells. Other fractions stimulated cell proliferation in the larval fat body cells.