Presence of unsaturated sphingomyelins and changes in their composition during the life cycle of the moth Manduca sexta

Abstract

NMR and electrospray ionization tandem mass spectrometry were used to show for the first time the presence of sphingomyelins in extracts of the tobacco hornworm Manduca sexta ( Lepidoptera ). The sphingosine in the ceramide was identified as tetradecasphing-4-enine, and the fatty acids were C18:0, C20:0, C22:0, and C24:0 (compound 1). Heterogeneity in the ceramide was observed in sphingomyelins from M. sexta. All of the sphingomyelins were associated with their doubly unsaturated sphingosine, tetradecasphing-4,6-dienine (compound 2), which contained the same set of fatty acids as compound 1 and represents a novel set of sphingomyelins not previously reported in Lepidoptera. Lipid rafts were isolated from brains of M. sexta, and the association of these novel sphingomyelins with rafts was confirmed. The existence of the additional double bond was also observed in ceramide and ceramide phosphoethanolamine isolated from M. sexta Interest in insect sphingosines as cell membrane constituents dates back to the 1960s (1), but three decades of work has provided information on this class of compounds for only a few insect species, namely, Musca domestica (2), Calliphora erythrocephala (3), Trogoderma granarium (4), Apis mellifera (5), and Aedes albopictus (6). Similarly, only limited information exists with regard to insect glycosphingolipids (GSLs, arthrosides). The mosquito Aedes aegypti (7), the green-bottle fly Lucilia caesar (8), the blowfly Calliphora vicina (9), and Drosophila melanogaster (10) have been studied, with no report of sphingomyelin in these species. Sphingomyelin is commonly found in small amounts as a cell membrane component in mammals and is present in myelinated nerve fibers in larger amounts, but its exact functions have yet to be elucidated in insects. Because ceramides and sphingosine-1-phosphate have been identified as important regulators of apoptosis, cell motility, and raft formation in mammals (11, 12), the absence of such molecules in insects would have serious implications, inasmuch as biochemical pathways in insects and vertebrates have generally been conserved over tens of millions of years.In his review on insect glycolipids, Wiegandt (13) stated that insect ceramides typically consist of C14:1 and C16:1 sphingosines, which are shorter than mammalian bases of 18 carbons or longer. The fatty acids reported at that time were C18:0, C20:0, and C22:0. The sphingolipids isolated from Dipteran differed from vertebrate sphingolipids, and the presence of sphingomyelin was not reported.The characterization of sphingosine derivatives is challenging, inasmuch as they typically constitute far less than 1% of the total lipid content of a tissue sample (14). Previously, time-consuming chemical decomposition methods and chemical derivatization were required for structural elucidation of the lipid and phospholipids of Manduca sexta (15). More recently, electrospray ionization-tandem mass spectrometry (ESI-MS/MS) was employed by Hsu Abbreviations: CID, collision-induced dissociation; COSY, cor...

Survival strategies of a sterol auxotroph

“…S5 in the supplementary material). Lipids with a similar sphingadiene LCB have been described in Drosophila (Fyrst et al, 2008) and Manduca (Abeytunga et al, 2004). Interestingly, a significant proportion of these sphingolipids contained N-amide-bound fatty acids that were a-hydroxylated (Fig.…”

Identification and characterization by electrospray mass spectrometry of endogenous Drosophila sphingadienes

“…we identified a family of endogenous sphingolipids containing a D 4,6 -sphingadiene LCB. Although not studied extensively, D 4,6 -sphingadienes have been reported in insect species, indicating that these structures may be conserved among dipteran insects (19,20). In contrast, sphingadiene LCBs, with the double bonds at C4 and C8, have been identified in numerous species.…”

“…In both studies, the D 4,6 -sphingadiene-containing ceramides were found to have potent although diverse biological effects. The ceramide compound from M. sexta was found to increase apoptosis in an embryonic M. sexta cell line (19), whereas the compound from B. mori was shown to promote neurite outgrowth in the rat pheochromocytoma cell line PC12 (20).…”

“…The presence of sphingolipids containing a D 4,6 -sphingadiene LCB has been reported in other insect species. A study of sphingomyelins from the tobacco hornworm Manduca sexta revealed the presence of D 4,6 -sphingadiene LCBs in sphingomyelin, ceramide-phosphoethanolamine, and ceramide (19). Moreover, a ceramide compound purified from larvae of the silk moth Bombyx mori was shown to contain a D 4,6 -sphingadiene LCB (20).…”

Characterization of a Germination-Accelerating Factor from the Silkworm (Bombyx moriLinnaeus) of Entomopathogenic FungusNomuraea rileyi(Farlow) Samson

“…However, direct recognition of sphingosines by N. rileyi conidia requires the expression of sphingosine receptors on the surface components of conidia (the rodlet layer 18) ), so sphingosine receptors may belong to a new type of receptor family. Almost all sphingoid bases from insects (Drosophila melanogaster, 19) Drosophila sphingadienes, 20) and Manduca sexta 21) ), which are not known as hosts of N. rileyi, carry 14 carbon atoms in the structure of the sphingoid base. Since 18 and 20 carbon atoms of the sphingoid base are commonly found in mammalian 22,23) and yeast cells, [24][25][26] 14 carbon atoms of the sphingoid base appear to be insect-specific.…”