title: Endocytotic routes of cobra cardiotoxins depend on spatial distribution of positively charged and hydrophobic domains to target distinct types of sulfated glycoconjugates on cell surface.
abstract: Cobra cardiotoxins (CTX) are a family of three-fingered basic polypeptides known to interact with diverse targets such as heparan sulfates, sulfatides, and integrins on cell surfaces. After CTX bind to the membrane surface, they are internalized to intracellular space and exert their cytotoxicity via an unknown mechanism. By the combined in vitro kinetic binding, three-dimensional x-ray structure determination, and cell biology studies on the naturally abundant CTX homologues from the Taiwanese cobra, we showed that slight variations on the spatial distribution of positively charged or hydrophobic domains among CTX A2, A3, and A4 could lead to significant changes in their endocytotic pathways and action mechanisms via distinct sulfated glycoconjugate-mediated processes. The intracellular locations of these structurally similar CTX after internalization are shown to vary between the mitochondria and lysosomes via either dynamin2-dependent or -independent processes with distinct membrane cholesterol sensitivity. Evidence is presented to suggest that the shifting between the sulfated glycoconjugates as distinct targets of CTX A2, A3, and A4 might play roles in the co-evolutionary arms race between venomous snake toxins to cope with different membrane repair mechanisms at the cellular levels. The sensitivity of endocytotic routes to the spatial distribution of positively charged or hydrophobic domains may provide an explanation for the diverse endocytosis pathways of other cell-penetrating basic polypeptides.
authors.affiliation: From the School of Medicine, FuJen Catholic University, Xinzhuang District, New Taipei City, 24205, Taiwan.
authors.forename: Shao-Chen
authors.initials: SC
authors.lastname: Lee
authors.affiliation: the Department of Life Sciences and Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, 30013, Taiwan, the Institute of Biological Chemistry, Academia Sinica, Taipei, 11529, Taiwan.
authors.forename: Chien-Chu
authors.initials: CC
authors.lastname: Lin
authors.affiliation: the Department of Life Sciences and Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, 30013, Taiwan.
authors.forename: Chia-Hui
authors.initials: CH
authors.lastname: Wang
authors.affiliation: the Department of Life Sciences and Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, 30013, Taiwan.
authors.forename: Po-Long
authors.initials: PL
authors.lastname: Wu
authors.affiliation: the Department of Life Sciences and Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, 30013, Taiwan.
authors.forename: Hsuan-Wei
authors.initials: HW
authors.lastname: Huang
authors.affiliation: the Institute of Biological Chemistry, Academia Sinica, Taipei, 11529, Taiwan.
authors.forename: Chung-I
authors.initials: CI
authors.lastname: Chang
authors.affiliation: the Department of Life Sciences and Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, 30013, Taiwan, lswwg@life.nthu.edu.tw.
authors.forename: Wen-guey
authors.initials: WG
authors.lastname: Wu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004179:Cobra Cardiotoxin Proteins / Q000737:chemistry* / Q000235:genetics / Q000493:pharmacokinetics*; D006224:Cricetinae; D003412:Cricetulus; D018360:Crystallography, X-Ray; D017815:Elapidae / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis; D019143:Evolution, Molecular; D006001:Glycoconjugates / Q000737:chemistry / Q000378:metabolism; D006497:Heparan Sulfate / Q000737:chemistry / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D054730:Protein Interaction Domains and Motifs; D051381:Rats; D055672:Static Electricity; D040681:Structural Homology, Protein
chemical_list: D004179:Cobra Cardiotoxin Proteins; D006001:Glycoconjugates; D006497:Heparan Sulfate
keywords: Cardiotoxin; Cholesterol; Endocytosis; Heparan Sulfate; Snake Venom; Sulfatide; X-ray Crystallography