Immunocytochemical localization and secretion process of the toxin CSTX-1 in the venom gland of the wandering spider Cupiennius salei (Araneae: Ctenidae)

Abstract

Fluorescein and horseradish peroxidase-labeled monoclonal antibodies were used to localize the predominant toxic peptide CSTX-1 in the venom gland of the spider Cupiennius salei. There was no polarity of CSTX-1 expression in repleted glands, whereas the glands of previously milked spiders showed a decreasing immunofluorescent response from the distal to the proximal portion. Detailed investigation revealed a new structure in the venom-secreting epithelium, which is postulated to be an evolutionary adaptation to increasing gland volume. CSTX-1 was found to be synthesized and stored as a fully active toxin within complex units, composed of long interdigitating cells running perpendicular to the muscular sheath and extending into the central lumen of the gland. These venom-producing units were found in all sectors of the gland, including the transitional region between the main gland and the venom duct. The venom is liberated from the venom-producing units into the glandular lumen following the contraction of the surrounding muscle layer. Free nuclei or other cellular fragments, which would have provided evidence for a holocrine secretion process, were not found in the glandular lumen or in the crude venom obtained by electrical stimulation. The fine regulation of the spider's venom injection process is postulated to be the function of the bulbous ampulla, situated in the anterior third of the venom duct.

A lysine rich C-terminal tail is directly involved in the toxicity of CSTX-1, a neurotoxic peptide from the venom of the spiderCupiennius salei

“…The present results suggest that these proteases occur in the venom gland and are released with the venom. The histological investigation of the venom gland structure of C. salei (Malli et al, 2000) indicates that these glands belong to the apocrine secretion type. This means that the secretion cells release membrane-bound vesicles filled with toxin into the lumen of the gland.…”

Venom apparatus of the Brazilian tarantula Vitalius dubius Mello-Leitão 1923 (Theraphosidae)

“…However, regardless of the variations in general organization, the secretory epithelium of spider venom glands contains abundant endoplasmic reticulum, autophagic vacuoles, mitochondria, and cytoplasmic vesicles with secretory material. As in other spiders (Malli et al 2000;dos Santos et al 2000), the epithelial cells of V. dubius show extensive interdigitations and close contact with each other.…”

“…Whereas the venom glands of many spiders are cylindrical (or variations of this; Malli et al 2000;Cavusoglu et al 2004Cavusoglu et al , 2005Yigit et al 2004;Yigit and Guven 2006) and may be single lobed, bilobular, or multilobular, others may be bulbous (Loxosceles intermedia Mello-Leitão 1934;dos Santos et al 2000;Loxosceles reclusa Gertsch and Mulaik 1940;Foil et al 1979) or ampoule-like (Phoneutria nigriventer Keyserling 1891Bücherl 1971;Silva et al 2008) in shape. In addition, the musculature surrounding the gland may form irregular bundles or lobes (L. reclusa; Foil et al 1979) or may be spiraled, as in V. dubius and other species, e.g., Cupiennius salei Keyserling 1877 (Malli et al 2000), Latrodectus mactans Fabricius 1775 (Smith and Russell 1967), Agelena labyrinthica Clerck 1757 (Yigit et al 2004;Yigit and Guven 2006), Allopecosa fabilis Clerck 1757 and Larinoides cornutus Clerck 1757 (Cavusoglu et al 2005). The venom gland of V. dubius consists of a complex network of epithelial cells surrounded by an elastin-rich basal layer and a series of muscle bundles distinct from the cheliceral muscles involved in cheliceral and fang movements.…”

“…Venom biosynthesis and the associated ultrastructural alterations during venom replenishment in spiders are generally less well understood than in other venomous animals such as snakes (Kochva 1978;Bdolah 1979), although immunocytochemistry has been used to investigate the glandular distribution and biosynthetic pathway of specific toxins, e.g., α-latrotoxin in L. tredecimguttatus (Cavalieri et al 1990) and CSTX-1 in C. salei (Malli et al 2000). As in other venomous animals (including scorpions and snakes), a variety of factors such as age (Malli et al 1993;Herzig et al 2004), sex (Célérier et al 1993;Andrade et al 1999;Oliveira et al 1999;Herzig et al 2002), hunger and breeding temperature (Vapenik and Nentwig 2000), season (Keegan et al 1960;Atkinson and Walker 1985), geographic origin (Binford 2001), and the frequency of milking (Perret 1977;Atkinson 1981) and feeding (Atkinson and Walker 1985) influence venom biosynthesis in spiders, with prey size being an important determinant of venom expenditure in some species, e.g., C. salei (Wigger et al 2002;Kuhn-Nentwig et al 2004).…”

The Strategic Use of Venom by Spiders

“…The ability to use or withhold venom independent from fang use stems from spider anatomy. The venom glands are surrounded by striated muscle under nervous control, allowing the deployment of venom via muscular contraction of the gland at the volition of the spider (Boeve et al 1995;Bucherl 1971;Malli et al 2000;Schenberg and Pereira-Lima 1978). In the context of predation, the interplay between prey size, prey defensive capabilities, and capacity of prey to struggle will influence whether spiders deploy their venom.…”