Elsevier

Journal of Proteomics

Volume 119, 24 April 2015, Pages 196-208
Journal of Proteomics

Proteomic analysis of the skin of Chinese giant salamander (Andrias davidianus)

https://doi.org/10.1016/j.jprot.2015.02.008Get rights and content

Highlights

  • We firstly reported the proteomes from skin, mucus and molting of Chinese giant salamander.

  • 249 proteins were identified in the skin, 155 in the mucus and 97 in the molting.

  • We found that many kinds of proteins were associated with immunity defense and wound healing.

  • Several proteins identified in the skin were related to respiration.

  • This study provided valuable information for the field of herpetology.

Abstract

The Chinese giant salamander (Andrias davidianus), renowned as a living fossil, is the largest and longest-lived amphibian species in the world. Its skin has developed mucous gland which could secrete a large amount of mucus under the scraping and electric stimulation, and the molting is the degraded skin stratum corneum. Although several proteomic studies have focused on functional proteomes of mammalian and frog skin, the skin proteome of Chinese giant salamander has not yet been carefully studied. To establish the functional skin proteome of Chinese giant salamander, two-dimensional gel electrophoresis (2DE) and mass spectrometry (MS) were applied to detect the composition and relative abundance of the proteins in the skin, mucus and molting. Our findings indicated that 249 proteins were identified in the skin, 155 proteins in the mucus, and 97 proteins in the molting. Furthermore, Gene Ontology (GO) analysis showed that these proteins participated in various physiological activities, including extracellular matrix organization, defense, immune response, wound healing, respiration, etc. In conclusion, the proteomic results provide new insight in the aspects of the proteomes in the skin, mucus and the molting of Chinese giant salamander.

Biological significance

This was the first study to examine the protein expression abundance in the skin, mucus and molting of Chinese giant salamander by a proteomics approach. Meantime, the identification of a more global proteome in normal skin may provide a basis for characterizing and comparing the skin proteomes from other amphibian species.

Introduction

The Chinese giant salamander (Andrias davidianus), belonging to order Caudata, family Cryptobranchidae, is the largest extant amphibian species. It occurs mostly in southwestern and eastern China and is classified as a class II protected species in China [1] and as one of the top 10 “focal species” by the Evolutionarily Distinct and Globally Endangered (EDGE) project in 2008 (http://www.edgeofexistence.org/). It is renowned as a living fossil, since it has been in existence for more than 350 million years [2], [3]. The evolution history of this species likely involves adaptations [4], [5], and its ancestral organisms may have represented transition steps from aquatic to terrestrial life, so this species has an important value in scientific research of skin system.

The skin of Chinese giant salamander is dark brown, black or greenish in color and irregularly blotched. It is also rough, wrinkled and porous which facilitates respiration through the skin as this large amphibian lacks gills. The skin is a multi functional organ acting in defense and cutaneous respiration [6], and is covered in mucus which protects their bodies from abrasions and parasites. When irritated or grasped, giant salamanders produce a milky, sticky secretion with heavy and astringency smell owing to its developed mucous gland. The main ingredients of skin mucus are sticky glycoproteins and fiber materials. Generally, the mucous secretions have antibacterial, antioxidation, antitumor, fatigue-resistant, and strengthened immunity [7], [8], [9]. Like other amphibians, this salamander has smooth skin that lacks scales, and the molting is the normal metabolism of the skin. Molting is a process of constant renewal of the outer layer of epidermis (stratum corneum) in amphibians, which provides a barrier against injury, pathogens and evaporative water loss [10]. In the private sector, the powder of giant salamander molting mixed with tung oil was utilized to treat burns [11]. In view of these characteristics, the research on Chinese giant salamander skin has important scientific significance. Therefore, it is of great interest to elucidate the proteome of its skin, mucus and molting. On the other hand, there is an urgent need to understand the defense reaction of Chinese giant salamander skin, due to the fact that a dramatic decline in the population has resulted from emerging infectious diseases [12], [13].

Despite the high public profile of Chinese giant salamander and their unique life-history characteristics, this species remains poorly characterized at the molecular level. Fortunately, proteomics can provide a global and comprehensive approach to the identification and description of biochemical processes at the protein level. Although several proteomic studies have focused on functional proteome of the human and mouse skin [14], [15], [16] and on the skin secretome of the frog [17], [18], the comprehensive proteomic profiling of Chinese giant salamander skin, is still unknown. This present study attempts to employ large-scale proteomic analysis to establish the functional proteome in the skin, mucus and molting of Chinese giant salamander. We identified 249 proteins in the skin, 155 proteins in the mucus, and 97 proteins in the molting using two-dimensional gel electrophoresis (2DE) coupled with mass spectrometry (MS). Gene Ontology (GO) analysis showed that these proteins participated in various physiological activities, including extracellular matrix organization, defense, immune response, wound healing, respiration, etc. This study provides some interesting new insights in the proteomes of the skin, mucus and molting of Chinese giant salamander, and may also provide a basis for characterizing and comparing the skin proteomes from other amphibian species.

Section snippets

Animals

Three or four year old male healthy Chinese giant salamanders with body length of 60–100 cm and weight of about 3 kg, were obtained from a giant salamander breeding base in Wen Quan Zhen, Kaixian Country, Chongqing Municipality, China. The molting was obtained from the breeding pool of Chinese giant salamanders. The mucus was secreted by the dorsal skin of Chinese giant salamanders under the scraping stimulation with a triangle, and was collected in a sterile tube. Subsequently, they were

Histology of the Chinese giant salamander skin

Chinese giant salamanders (Fig. 1A and B) were obtained from a giant salamander breeding base, and Chinese giant salamander with the secreted mucus was shown in Fig. 1B. Moreover, the histological appearance of the skin tissue in transverse section was shown in Fig. 1C. The organizational structure of the skin is composed of three basic layers: the epidermal layer, the dermal layer, and the subcutaneous layer. The epidermal layer is made up of 2–5 layers of skin cells and the outer-most layer

Discussion

The Chinese giant salamander (A. davidianus), renowned as a living fossil, is the largest extant tailed amphibian species in the world [2], [3]. The number of Chinese giant salamander is in global decline, with extinction threats coming from various sources, not only from environmental disruption, predation and pollution, but also from fungal and viral pathogens [12], [13]. Understanding the susceptibility of giant salamander to these pathogens is a major challenge. Giant salamander skin

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Acknowledgments

This work was supported by grants from the National Basic Research 973 Pre-research Program of China (No. 2012CB722304), the Major Scientific and Technological Projects of Henan (111100910600), and the Foundation and Advanced Technology Research Program of Henan (No. 132300413208, No. 132300410134 and No. 142300413212).

References (56)

  • M. Mechkarska et al.

    Peptidomic analysis of skin secretions demonstrates that the allopatric populations of Xenopus muelleri (Pipidae) are not conspecific

    Peptides

    (2011)
  • D. Krug et al.

    Minor cartilage collagens type IX and XI are expressed during embryonic stem cell-derived in vitro chondrogenesis

    Ann Anat

    (2013)
  • R.P. Boot-Handford et al.

    A novel and highly conserved collagen (pro(alpha)1(XXVII)) with a unique expression pattern and unusual molecular characteristics establishes a new clade within the vertebrate fibrillar collagen family

    J Biol Chem

    (2003)
  • L.A. Rollins-Smith

    The role of amphibian antimicrobial peptides in protection of amphibians from pathogens linked to global amphibian declines

    Biochim Biophys Acta

    (2009)
  • C. Guo et al.

    Identification of multiple peptides with antioxidant and antimicrobial activities from skin and its secretions of Hylarana taipehensis, Amolops lifanensis, and Amolops granulosus

    Biochimie

    (2014)
  • W.M. Holden et al.

    Development of antimicrobial peptide defenses of southern leopard frogs, Rana sphenocephala, against the pathogenic chytrid fungus, Batrachochytrium dendrobatidis

    Dev Comp Immunol

    (2015)
  • R. Zhu et al.

    Thymus cDNA library survey uncovers novel features of immune molecules in Chinese giant salamander Andrias davidianus

    Dev Comp Immunol

    (2014)
  • R. Zhu et al.

    Extensive diversification of MHC in Chinese giant salamanders Andrias davidianus (Anda-MHC) reveals novel splice variants

    Dev Comp Immunol

    (2014)
  • B. Zhu et al.

    Brief report. The karyotype of the caudate amphibian Andrias davidianus

    Hereditas

    (2002)
  • K.Q. Gao et al.

    Earliest known crown-group salamanders

    Nature

    (2003)
  • K.Q. Gao et al.

    Late Jurassic salamanders from northern China

    Nature

    (2001)
  • E. Heiss et al.

    Biomechanics and hydrodynamics of prey capture in the Chinese giant salamander reveal a high-performance jaw-powered suction feeding mechanism

    J R Soc Interface

    (2013)
  • L. Wang et al.

    Characterization and bioactivity of antimicrobial peptides from the skin secretions of the Andrias davidianus

    Chin J Biochem Pharmacol

    (2011)
  • W. Guo et al.

    Major biological activities of the skin secretion of the Chinese giant salamander, Andrias davidianus

    Z Naturforsch C

    (2012)
  • W. Guo et al.

    Skin secretion and shedding is a good source for non-destructive genetic sampling in the Chinese giant salamander (Andrias davidianus)

    Z Naturforsch C

    (2013)
  • T.M. Triana et al.

    Ontogenetic comparison of the molting frequency in Rhinella marina (Anura: Bufonidae)

    Iheringia Ser Zool

    (2013)
  • J. Guo et al.

    The anti-inflammatory and analgesic action of the skin powder of Andrias davidianus

    Henan Tradit Chin Med

    (2013)
  • W. Dong et al.

    Iridovirus infection in Chinese giant salamanders, China, 2010

    Emerg Infect Dis

    (2011)
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