Biosynthetic route of locust apolipophorin III isoforms.
Insect apolipophorin III (apoLp-III) plays a key role in the enhanced diacylglycerol transport during insect flight. For apoLp-III of the migratory locust, two different isoforms have been described (apoLp-IIIa and -b), displaying different N-termini and isoelectric points; each of the isoforms is however equally well capable to perform its function in lipid transport. In the present report the biosynthetic route of the apoLp-III isoforms is elucidated. Immunoprecipitation of media from in vitro fat body incubations and analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that the locust fat body synthesized and secreted apoLp-III. ApoLp-III levels in the hemolymph showed that in young adults, apoLp-III concentrations were only very low (1-3 mg/ml). During adult maturation, however, the apoLp-III concentration increased rapidly to approximately 17 mg/ml. During apoLp-III elevation, the apoLp-IIIa:-b ratio remained equal or in the favour of the a-isoform, while in adults from approximately 12 days after adult ecdysis apoLp-IIIb was the most abundant isoform. Analysis of the protein by native polyacrylamide gel electrophoresis showed that only the apoLp-IIIa form was secreted. Injection of radiolabeled apoLp-IIIa into the hemolymph of adult locusts resulted in a slow conversion into apoLp-IIIb.
Weers
P M
PM
Department of Experimental Zoology, University of Utrecht.
Van Baal
J
J
Van Doorn
J M
JM
Ziegler
R
R
Van der Horst
D J
DJ
D000818:Animals; D001053:Apolipoproteins / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005216:Fat Body / Q000378:metabolism*; D006110:Grasshoppers / Q000254:growth & development / Q000378:metabolism*; D006458:Hemolymph / Q000378:metabolism; D066298:In Vitro Techniques; D008970:Molecular Weight; D011233:Precipitin Tests
D001053:Apolipoproteins; D002352:Carrier Proteins; C042470:apolipophorin III