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Dr. Antônio Guilherme De Souza” Instituto Butantan Secretaria de Estado da Saúde de São Paulo Centro de Formação de Recursos Humanos para o SUS/SP “Dr. Antônio Guilherme de Souza” Instituto Butantan RAFAEL DE OLIVEIRA Toxinas animais seletivas a canais iônicos: uma revisão. São Paulo 2020 Rafael de Oliveira Toxinas animais seletivas a canais iônicos: uma revisão. Trabalho de conclusão de curso de especialização apresentado ao Instituto Butantan, unidade do Centro de Formação de Recursos Humanos para o SUS/SP “Doutor Antônio Guilherme de Souza”, como requisito parcial para a obtenção do título de Especialista em Toxinas de Interesse em Saúde. Orientador (a): Dr. Lanfranco Ranieri Paolo Troncone. São Paulo 2020 Oliveira, Rafael de Toxinas animais seletivas a canais iônicos: uma revisão. / Rafael de Oliveira; orientador Lanfranco Ranieri Paolo Troncone. – São Paulo, 2020. 48 f.: il. Trabalho de Conclusão de Curso (Especialização) – Secretaria de Estado da Saúde, Centro de Formação de Recursos Humanos para o SUS/SP “Doutor Antônio Guilherme de Souza” desenvolvido no Instituto Butantan para o Curso de Especialização em Toxinas de Interesse em Saúde. 1. Toxinologia. 2. Canais iônicos. I. Oliveira, Rafael de. II. Instituto Butantan. III. Curso de Especialização em Toxinas de Interesse em Saúde. IV. Título. AGRADECIMENTOS Meus sinceros e eternos agradecimentos: A meu orientador Dr Lanfranco Ranieri Paolo Troncone, pelo tempo, dedicação e aprendizado a mim fornecidos. A Dra Raif Musa Aziz e suas alunas, pela ajuda e disponibilidade. A Janaína Paola Schwerz e seus estagiários, pela aventura neurocientífica. A Aline, Lívia e Rafaela, as muçuranas do serpentário. Ao Pep V, pelas histórias e o ano de 2020. A minha companheira Rita de Cássia, pelas palavras e balas Fini (menos as de amora). A todos meus amigos e familiares que estiveram presentes nesta jornada. E ao Ernesto. “[...] I have completed this story. I do not consider myself less ignorant than most people. I have been and still am a seeker, but I have ceased to question stars and books. I have begun to listen to the teachings my blood whispers to me.” Hermann Hesse RESUMO OLIVEIRA, Rafael de. Toxinas animais seletivas a canais iônicos: uma revisão. 2020. 48 p. Trabalho de Conclusão de Curso (Especialização em Toxinas de Interesse em Saúde) – Centro de Formação de Recursos Humanos para o SUS/SP; Instituto Butantan, São Paulo, 2020. Venenos animais são secreções glandulares que comprometem sistemas biológicos. Suas biomoléculas ativas são denominadas toxinas. Muitas afetam canais iônicos e receptores ionotrópicos, proteínas de membrana que controlam o fluxo iônico celular. Neste trabalho foi realizado um levantamento bibliográfico sobre as principais toxinas de origem animal cujos alvos são canais iônicos. Os grupos com maior diversidade de toxinas foram Conus ssp., Araneae, Scorpiones, Serpentes e Cnidaria. Estudos sobre toxinas auxiliam a ciência de base e aplicada. Apesar do potencial terapêutico, dentre todos os venenos estudados apenas a ω-conotoxina MVIIA obteve aprovação para o uso clinico. Portanto, o campo ainda tem muito a oferecer. Palavras-chave: Canais iônicos. Peptídeos. Receptores ionotrópicos. Toxinologia. Venenos. ABSTRACT OLIVEIRA, Rafael de. Ion channels selective animal toxins: a review. 2020. 48 p. Monograph (Specialization in Toxins of Interest in Health) – Centro de Formação de Recursos Humanos para o SUS/SP; Instituto Butantan, São Paulo, 2020. Animal poisons are glandular secretions that compromise biological systems. Their active biomolecules are called toxins. Many affect ion channels and ionotropic receptors, membrane proteins that control cellular ion flow. In this work a bibliographic survey was carried out about the main toxins of animal origin whose targets are ion channels. The groups with the highest toxin diversity were Conus ssp., Araneae, Scorpiones, Serpentes and Cnidaria. Toxins studies support basic and applied science. Despite their therapeutic potential, of all the studied poisons only ω-conotoxin MVIIA was approved for clinical use. So the field still has a lot to offer. Keywords: Ion channels. Peptides. Ionotropic receptors. Toxinology. Venons. LISTA DE SIGLAS E ABREVIAÇÔES AMPAR Receptor de ácido α-amino-3-hidroxi-metil-4-isoxazolepropiônico ASIC Canal iônico sensível a ácidos BKCa Canal de potássio ativado por cálcio de condutância alta CaV Canal de cálcio voltagem dependente CFTR Regulador de condutância transmembranar de fibrose cística CNG Canal com portão de nucleotídeo ciclíco ClC Canal de cloreto voltagem dependente EC50 Metade da concentração efetiva GABAA Receptor ionotrópico de ácido γ-aminobutírico do tipo A HCN Canal para cátions ativado por hiperpolarização e nucleotídeo cíclico IKCa Canal de potássio ativado por cálcio de condutância intermediária K2p Canal de potássio com domínio de dois poros KCa Canal de potássio ativado por cálcio Kir Canal de potássio retificador interno KV Canal de potássio voltagem dependente KR Receptor de cainato NaV Canal de sódio voltagem dependente nAChR Receptor de acetilcolina nicotínico NMDAR Receptor ionotrópico de N-metil-D-aspartato SKCa Canal de potássio ativado por cálcio de condutância baixa TRP Receptor de potencial transiente SUMÁRIO 1. Introdução ..................................................................................................... 11 2. Objetivos ....................................................................................................... 13 3. Metodologia .................................................................................................. 13 4. Resultados .................................................................................................... 13 5. Discussão ..................................................................................................... 21 5.1. Canais de sódio ...................................................................................... 21 5.2. Canais iônicos sensíveis a ácidos........................................................ 22 5.3. Canais de potássio ................................................................................. 23 5.4. Canais de cálcio ..................................................................................... 24 5.5. Canais de cloreto ................................................................................... 25 5.6. Transportadores ABC ............................................................................ 25 5.7. Receptores colinérgicos ........................................................................ 26 5.8. Receptores GABAérgicos ..................................................................... 26 5.9. Receptores glutamatérgicos ................................................................. 27 5.10. Receptores serotonérgicos ................................................................ 28 5.11. Receptores de potencial transitório .................................................. 28 5.12. Outros tipos ......................................................................................... 29 5.13. Perspectivas futuras ........................................................................... 30 6. Conclusão ..................................................................................................... 33 REFERÊNCIAS ..................................................................................................... 34 11 1. Introdução Venenos animais são secreções de glândulas especializadas que alteraram a funcionalidade de sistemas biológicos. Usualmente contêm enzimas (oxidases e hidrolases), sais, proteínas (three-finger-toxins, desintegrinas, fatores de crescimento, etc.), peptídeos e outros compostos orgânicos (UTKIN, 2015). Exercem função de forrageio e defesa. Venenos defensivos tendem a possuir alvos moleculares fixos, enquanto venenos predatórios são mais variantes (CASEWEL et al., 2013). Toxinas, do grego toxikón - “veneno para flechas”, são substâncias de origem biológica que exercem efeito deletério em outros seres vivos. Classificam-se de acordo com a espécie de origem e o efeito no organismo afetado. São produzidas por micro-organismos, plantas, fungos e metazoários (KLAASSEN et al., 2013). Compõem a porção bioativa dos venenos. Tipicamente toxinas não-peptídicas se perpetuam via oral enquanto toxinas peptídicas são inoculadas por animais com aparatos especializados (LEWIS & GARCIA, 2003). Diversos táxons possuem animais venenosos, como cnidários, moluscos, artrópode, répteis e mamíferos. Apesar da diversidade de espécies, pressões seletivas induziram classes distintas de toxinas a afetarem os mesmos alvos moleculares (FRY et al., 2009). Algumas famílias gênicas de toxinas são extremamente conservadas, enquanto outras possuem perfil variável, resultando em uma vasta diversidade de tipos (DUDA & PALUMBI, 1999). Estudos corroboram o papel da dinâmica evolutiva entre presa e predador no desenvolvimento de toxinas, apoiando a hipótese da Rainha Vermelha (CASEWEL et al., 2013). Pressões seletivas podem favorecer o animal a desenvolver resistências ao ponto de causar mutações e expressões de antivenenos (BIARDI et al., 2011; CASEWEL et al., 2013). Em contra partida, o mesmo processo potencializa as toxinas de animais venenosos. Toxinas agem em uma infinitude de alvos intra e extracelulares, englobando enzimas, canais iônicos, receptores de membrana e outras estruturas (MÉNEZ et al., 2006). Canais iônicos são proteínas de membrana formadoras de poros, cuja conformação espacial se altera com o potencial elétrico da membrana celular, modificando sua permeabilidade
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