Acidification of yolk granules in <i>Blattella germanica</i> eggs coincident with proteolytic processing of vitellin

Nordin, John H.; Beaudoin, Esther; Liu, Xiaodong

doi:10.1002/arch.940180306

Cited by 50 publications

(50 citation statements)

References 37 publications

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“…It is, therefore, likely that the presence of both these proenzymes in the matrix surrounding crystalline Vn enhances their rapid activation at the onset of embryonic development, the point at which yolk bodies undergo acidification. The latter event has been documented for both insects and vertebrates (74,75).…”

Section: Discussionmentioning

confidence: 88%

Mosquito Cathepsin B-like Protease Involved in Embryonic Degradation of Vitellin Is Produced as a Latent Extraovarian Precursor

Cho

Tsao

Hays

et al. 1999

Journal of Biological Chemistry

185

126

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Here we report identification of a novel member of the thiol protease superfamily in the yellow fever mosquito, Aedes aegypti. It is synthesized and secreted as a latent proenzyme in a sex-, stage-, and tissue-specific manner by the fat body, an insect metabolic tissue, of female mosquitoes during vitellogenesis in response to blood feeding. The secreted, hemolymph form of the enzyme is a large molecule, likely a hexamer, consisting of 44-kDa subunits. The deduced amino acid sequence of this 44-kDa precursor shares high similarity with cathepsin B but not with other mammalian cathepsins. We have named this mosquito enzyme vitellogenic cathepsin B (VCB). VCB decreases to 42 kDa after internalization by oocytes. In mature yolk bodies, VCB is located in the matrix surrounding the crystalline yolk protein, vitellin. At the onset of embryogenesis, VCB is further processed to 33 kDa. The embryo extract containing the 33-kDa VCB is active toward benzoyloxycarbonyl-ArgArg-para-nitroanilide, a cathepsin B-specific substrate, and degrades vitellogenin, the vitellin precursor. Both of these enzymatic activities are prevented by transepoxysuccinyl-L-leucylamido-(4-guanidino)butane (E-64), a thiol protease inhibitor. Furthermore, addition of the anti-VCB antibody to the embryonic extract prevented cleavage of vitellogenin, strongly indicating that the activated VCB is involved in embryonic degradation of vitellin.Cathepsin B is a thiol (cysteine) protease with both endopeptidase and peptidyldipeptidase activities. Due to its broad specificity, cathepsin B plays a key role in intracellular protein catabolism in the lysosomal system (1). Cathepsin B has been well characterized both enzymatically and molecularly (2-10). The mammalian cathepsin B has been implicated in tumor invasion, progression, and metastasis (11-15). Tumor-specific cathepsin B is secreted by malignant cells as a latent high molecular weight precursor, presumably activated at cell contacts (16,17).In addition, cathepsins B, as well as the related cathepsins L, have been identified in numerous parasitic protozoa and helminthes, including prevalent pathogens of human and domestic animals (18 -26). In the blood-sucking bug, Rhodnius prolixus, cathepsin B is the major gut proteolytic enzyme (27). In these organisms, cathepsins B and L are presumably involved in the degradation of host hemoglobin.In insects and other arthropods, cathepsins B and L also participate in key developmental processes. In the flesh fly, Sarcophaga peregrina, hemocytes produce the extracellular form of a cathepsin B-like enzyme that participates in decomposition of the larval fat body during metamorphosis (28 -30). Moreover, cathepsins B and L have been implicated in degradation of yolk proteins during embryonic development (31-41).The elucidation of developmental mechanisms in the mosquito is important because this insect transmits the most devastating of vector-borne human diseases, including malaria, lymphatic filariasis, Dengue fever, and many others. Little is known, however, about t...

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Section: Discussionmentioning

confidence: 88%

Mosquito Cathepsin B-like Protease Involved in Embryonic Degradation of Vitellin Is Produced as a Latent Extraovarian Precursor

Cho

Tsao

Hays

et al. 1999

Journal of Biological Chemistry

185

126

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“…Altogether, our results suggest that calcium-induced membrane fusion events take part in yolk degradation, leading to the assembly of the yolk mobilization machinery. (Fagotto, 1991;Nordin et al, 1991;Mallya et al, 1992;Fagotto, 1995) and proton pyrophosphatases (H + -PPases) (Motta et al, 2004). In insects, several hydrolytic enzymes found in YGs such as cathepsins (Takahashi et al, 1996;Cho et al, 1999;Ribolla et al, 2001), acid phosphatases (Nussenzveig et al, 1992;Ribolla et al, 1993;Fialho et al, 2002;Fialho et al, 2005) and glycosidases (Purcell et al, 1988) were shown to be activated by low pH.…”

Section: Introductionmentioning

confidence: 99%

Calcium-regulated fusion of yolk granules is important for yolk degradation during early embryogenesis of Rhodnius prolixusStahl

Ramos

Miranda

Souza

et al. 2007

Journal of Experimental Biology

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SUMMARY This study examined the process of membrane fusion of yolk granules (YGs)during early embryogenesis of Rhodnius prolixus. We show that eggs collected at days 0 and 3 after oviposition contain different populations of YGs, for example day-3 eggs are enriched in large YGs (LYGs). Day-3 eggs also contain the highest free [Ca2+] during early embryogenesis of this insect. In vitro incubations of day-0 YGs with [Ca2+]similar to those found in day-3 eggs resulted in the formation of LYGs, as observed in vivo. Fractionation of LYGs and small YGs (SYGs) and their subsequent incubation with the fluorescent membrane marker PKH67 showed a calcium-dependent transference of fluorescence from SYGs to LYGs, possibly as the result of membrane fusion. Acid phosphatase and H+-PPase activities were remarkably increased in day-3 LYGs and in calcium-treated day-0 LYGs. Both fractions were found to contain vitellins as major components, and incubation of YGs with calcium induced yolk proteolysis in vitro. Altogether, our results suggest that calcium-induced membrane fusion events take part in yolk degradation, leading to the assembly of the yolk mobilization machinery.

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“…Each vitellin polypeptide is degraded in a time-and stagespecific manner by the embryo (28,31,17). Enzymes specific for vitellin degradation have been identified and found to be activated upon the 197 attainment of certain stages of development (25,20,12). Evidence to date suggests that yolk utilization in insects is a highly ordered process, requiring specific gene expression (31,10) and perhaps specific cell-to-cell interaction to be developmentally regulated (1).…”

Section: Introductionmentioning

confidence: 99%

An Ultrastructural Investigation on Vitellophage Invasion of the Yolk Mass during and after Germ Band Formation in Embryos of the Stick Insect Carausius morosus Br.

Fausto¹,

Carcupino²,

Mazzini³

et al. 1994

Dev Growth Differ

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Developing embryos of the stick insect Carausius morosus were examined ultrastructurally with a view to studying vitellophage invasion of the yolk mass during and after germ band formation. Newly laid eggs in Cmorosus have a unique yolk fluid compartment surrounded by a narrow fringe of cytoplasm comprising several small yolk granules. Vitellophages originate mainly from a thin layer of stem cells, the so-called yolk cell membrane, interposed between the germ band and the yolk mass. Throughout development, a thin basal lamina separates the yolk cell membrane from the overlying embryo.Vitellophages extend from the yolk cell membrane with long cytoplasmic processes or filopodia to invade the central yolk mass. Along their route of entrance, filopodia engulf portions of the yolk mass and sequester it into membrane-bounded granules. As this process continues, the yolk mass is gradually partitioned into a number of yolk granules inside the vitellophages.Later in development, the yolk cell membrane is gradually replaced by the endodermal cells that emerge from the anterior and posterior embryonic rudiments. From this stage of development onwards, vitellophages remain attached to the basal lamina through long filopodia extending between the endodermal cells, Yolk confined in different vitellophagic cells appears heterogeneous both in density and texture, suggesting that yolk degradation may be spatially differentiated.

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Acidification of yolk granules in Blattella germanica eggs coincident with proteolytic processing of vitellin

Cited by 50 publications

References 37 publications

Mosquito Cathepsin B-like Protease Involved in Embryonic Degradation of Vitellin Is Produced as a Latent Extraovarian Precursor

Mosquito Cathepsin B-like Protease Involved in Embryonic Degradation of Vitellin Is Produced as a Latent Extraovarian Precursor

Calcium-regulated fusion of yolk granules is important for yolk degradation during early embryogenesis of Rhodnius prolixusStahl

An Ultrastructural Investigation on Vitellophage Invasion of the Yolk Mass during and after Germ Band Formation in Embryos of the Stick Insect Carausius morosus Br.

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