Cathepsin B-like proteinase is involved in the decomposition of the adult fat body ofHelicoverpa armigera

Abstract

Cathepsin B-like proteinase (HCB, EC 3.4.22.1) is expressed in Helicoverpa armigera oocytes and adult fat bodies. Previous work has revealed that HCB plays a key role in the degradation of yolk proteins during embryogenesis. This study investigated the function and regulatory activation of HCB in adult fat bodies during aging and oogenesis. The HCB transcript was detected at all stages from larval to adult fat bodies with Northern blot analysis. Pro-HCB was also detected in fat bodies at these stages with an immunoblot assay using a monoclonal antibody against HCB. However, mature HCB and its activity were only detected in fat bodies of pre-adults and adults. This evidence suggested that HCB is regulated post-translationally by activation of the pro-enzyme during the pupa-adult metamorphosis. The activation of HCB was coupled with the expression of hormone receptor 3 (HHR3), and was up-regulated by the ecdysteroid agonist, RH-2485, suggesting that HCB activation is related to the ecdysone regulatory system. The decomposition of the adult fat bodies during aging and oogenesis was found to occur via programmed cell death, in which HCB took part.

Cathepsins of lepidopteran insects: Aspects and prospects

“…In B. mori, CathL like protease is autocatalytically converted from its proenzyme of 47 to a 37 kDa active form in response to the acidification of yolk granules during embryogenesis (Kageyama and Takahashi, 1990;Takahashi et al, 1996;Yamahama et al, 2003;Yamamoto et al, 1999). Similarly, the proenzyme of H. armigera CathB was detected in the fat body throughout the life cycle, whereas active CathB was only observed in adult fat body (Yang et al, 2006;Zhao et al, 2005). Besides being critically important for development, cathepsins also function in processes like apoptosis and stress responses which adds to their physiological roles in the lepidopteran insects.…”

“…Also, inhibition of fat body apoptosis was indicated by a decrease in DNA fragmentation on silencing of CathB. Thus positive correlation between fat body histolysis and CathB expression was established (Yang et al, 2006). Likewise, the expression of CathD was closely associated with DNA fragmentation during the degradation of larval midgut and fat body cells of B. mori (Gui et al, 2006).…”

“…Simultaneously, it is overexpressed in the larval midgut which sustains in pupa till adult eclosion. However, in H. armigera, only CathB is reported to be involved in metamorphosis from pupae to adult (Yang et al, 2006). Thereafter, it is active in the adult fat bodies of both males and females, indicating its involvement in aging process where the fat body of moths is degraded.…”

Purification and characterization of two cysteine peptidases of the Mediterranean fruit fly Ceratitis capitata during metamorphosis

“…Cysteine peptidases were also involved in B. mori silk gland histolysis (Shiba et al, 2001) and in the decomposition of the adult fat body during aging and oogenesis (Yang et al, 2006). We previously determined that the fat body disintegration progresses in an anterior-posterior way (Rabossi et al, 2004).…”

Characteristics of protein variants in trichlorphon-resistant Bactrocera dorsalis (Diptera; Tephritidae) larvae

“…For example, Bombyx mori cathepsin B is involved in the programmed cell death of silk glands and results in the histolysis of silk glands during metamorphosis (Shiba et al, 2001). Helicoverpa armigera (Noctuidae, Lepidoptera) cathepsin B is involved in the degradation of yolk proteins during embryonic development (Zhao et al, 2005) and decomposition of adult fat bodies (Yang et al, 2006). The expression level of protein D3 is much higher than that expressed in 3 and 6 h after trichlorphon induction.…”