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Serratia entomophila and Serratia proteamaculans (Enterobacteriaceae) cause amber disease in the grass grub Costelytra zealandica (Coleoptera: Scarabaeidae), an important pasture pest in New Zealand. Larval disease symptoms include cessation of feeding, clearance of the gut, amber coloration, and eventual death. A 155-kb plasmid, pADAP, carries the genes sepA, sepB, and sepC, which are essential for production of amber disease symptoms. Transposon insertions in any of the sep genes in pADAP abolish gut clearance but not cessation of feeding, indicating the presence of an antifeeding gene(s) elsewhere on pADAP. Based on deletion analysis of pADAP and subsequent sequence data, a 47-kb clone was constructed, which when placed in either an Escherichia coli or a Serratia background exerted strong antifeeding activity and often led to rapid death of the infected grass grub larvae. Sequence data show that the antifeeding component is part of a large gene cluster that may form a defective prophage and that six potential members of this prophage are present in Photorhabdus luminescens subsp. laumondii TTO1, a species which also has sep gene homologues.

Receptor-activated phosphoinositide (PI) 3-kinases produce Ptdlns(3,4,5)P(sub 3) and its metabolite Ptdlns(3,4)P(sub 2) that function as second messengers in membrane recruitment and activation of target proteins. The cytohesin and centaurin protein families are potential targets for Ptdlns(3,4,5)P(sub 3) that also regulate and interact with Arf GTPases. Consequently, these families are poised to transduce PI 3-kinase activation into coordinated control of Arf-dependent pathways. Proposed downstream events in PI 3-kinaseregulated Arf cascades include modulation of vesicular trafficking and the actin cytoskeleton.

A protein receptor for inositol 1,3,4,5-tetrakisphosphate, Ins(1,3,4,5)P4, has been purified from stimulated cell tissue that specifically binds Ins(1,4,5)P3. The protein shows a specificity for Ins(1,3,4,5)P4's isomeric configuration and has a high affinity for it. The behavior the protein and its in vitro GAP activity against Ras and Rap indicate a GTPase-activating protein of the GAP1 family while Ras GAP activity is stimulated by Ins(1,3,4,5)P4 and inhibited by phospholipids.

Overexpression of mutant p85 alpha, lacking a binding site for P110, in Chinese hamster ovary (CHO) cell line inhibits the formation of a complex between tyrosine-phosphorylated insulin receptor substrate and 1-phosphatidylinositol 3-kinase. Inhibition leads to decreased insulin-stimulated accumulation of PI(3,4,5) P3 and glucose uptake, indicating the necessity of PI3-kinase for glucose transport in CHO cells. Inhibition has no influence on the RAS activation.