{"id":15,"date":"2019-01-30T15:42:30","date_gmt":"2019-01-30T15:42:30","guid":{"rendered":"https:\/\/geiselmed.dartmouth.edu\/bliska\/?page_id=15"},"modified":"2023-07-12T17:30:51","modified_gmt":"2023-07-12T17:30:51","slug":"research","status":"publish","type":"page","link":"https:\/\/geiselmed.dartmouth.edu\/bliska\/research\/","title":{"rendered":"Research"},"content":{"rendered":"

The long-term aim of research in the Bliska Lab is to understand how bacterial effectors that are secreted into infected leukocytes promote pathogenesis or elicit host protection. Our current research is focused on bacterial pathogens that use type III secretion (T3S) or type VI secretion (T6S) systems to deliver effectors into phagocytic leukocytes (macrophages, monocytes, neutrophils). Effectors are proteins, usually enzymes, that manipulate phagocyte processes to promote bacterial pathogenesis.\u00a0 The pathogenic activities of some effectors can induce an immune response in phagocytes by a mechanism referred to as effector-triggered immunity (ETI).\u00a0 A common mechanism of ETI involves assembly of a multiprotein complex called an inflammasome. Inflammasomes coordinate the processing and release of pro-inflammatory cytokines through pores formed in the plasma membrane of the phagocyte.\u00a0 Inflammasome activation can also lead to death of phagocytes by a process called pyroptosis, and dying neutrophils can extrude chromatin as extracellular traps (NETs). The following projects explore mechanisms of inflammasome regulation and ETI at the molecular, cellular and immunological levels in the Gram-negative bacterial pathogens Yersinia, Pseudomonas <\/em>and Burkholderia.<\/em><\/p>\n

Yersinia<\/em><\/strong>
\nYersinia <\/em>species (e.g. Y. pseudotuberculosis<\/em>) are<\/em> virulent bacteria that cause invasive infections (yersiniosis or plague) in healthy humans. Yersinia <\/em>are primarily extracellular pathogens that use T3S to deliver effectors across the plasma membrane of phagocytes.\u00a0 We study Yersinia<\/em> effectors that interact with the RhoA-pyrin signaling pathway in phagocytes. Two Yersinia<\/em> effectors (YopE, YopT) promote pathogenesis by inactivating RhoA, a small GTPase and regulator of cellular processes such as actin dynamics. Inactivation of RhoA by these effectors triggers an ETI in phagocytes in which the guard protein pyrin assembles an inflammasome. Because cytokine and NET release promotes host protection in this context, Yersinia <\/em>evolved a third effector (YopM) that inhibits the pyrin inflammasome, to block ETI. Current goals in this project are to determine how pyrin is positively and negatively regulated by Yersinia <\/em>effectors in phagocytes and the immunological basis of ETI.<\/p>\n

Pseudomonas<\/em><\/strong>
\nPseudomonas aeruginosa <\/em>is an opportunistic pathogen responsible for chronic lung infections in people with cystic fibrosis (CF). CF is a genetic disease associated with multiple immune deficiencies underlying the susceptibility to P. <\/em>aeruginosa <\/em>and other pathogens.\u00a0 P. <\/em>aeruginosa <\/em>is primarily an extracellular pathogen that uses T3S to deliver effectors across the plasma membrane of phagocytes.\u00a0 We study the effector ExoS which has broad substrate specificity and inhibits phagocytosis and superoxide production in neutrophils.\u00a0 ExoS is epidemiologically linked to successful establishment of P. <\/em>aeruginosa <\/em>infections in people with CF. Current goals in this project are to determine if ExoS regulates inflammasome responses and ETI in neutrophils infected with P. <\/em>aeruginosa. <\/em>We are also investigating the use of synthetic immunology to engineer phagocytes to function as immunotherapeutics targeting P. <\/em>aeruginosa.<\/em><\/p>\n

Burkholderia<\/em><\/strong>
\nBurkholderia <\/em>species (e.g. B. cenocepacia, B. orbicola<\/em>) are opportunistic pathogens that cause chronic inflammatory lung infections in people with CF. Burkholderia <\/em>are primarily intracellular pathogens that reside in macrophages after they are taken up by phagocytosis.\u00a0 Defects in superoxide production by CF macrophages may underlie the susceptibility of these cells to colonization by Burkholderia.<\/em> Burkholderia <\/em>use T6S to deliver the effector TecA across the phagosomal membrane.\u00a0 TecA inactivates RhoA, leading to assembly of the pyrin inflammasome in macrophages.\u00a0 We have determined that Burkholderia<\/em> triggers two additional inflammasome mechanisms in macrophages.\u00a0 Our results suggest that macrophage inflammasome responses to Burkholderia <\/em>in the lung is not protective and instead results in immunopathogenesis.\u00a0 We call this e<\/u>ffector-t<\/u>riggered immuno-p<\/u>athogenesis (ETP). Current goals in this project are to understand how TecA is delivered across the phagosome membrane,\u00a0 to define the ETP mechanisms caused by Burkholderia <\/em>in macrophages and the role of these processes in lung disease.<\/p>\n","protected":false},"excerpt":{"rendered":"

The long-term aim of research in the Bliska Lab has been to understand how bacterial effectors that are secreted into infected leukocytes promote pathogenesis or elicit host protection. Our current research is focused on bacteria that use type III or type VI secretion systems to deliver effectors into phagocytic leukocytes (monocytes, macrophages, neutrophils).<\/p>\n

Of particular interest are effectors that interact with the RhoA-pyrin signaling pathway in phagocytes. Several effectors promote pathogenesis by specifically inactivating RhoA, a small GTPase and regulator of cellular processes such as phagocytosis.<\/p>\n

Learn more »<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"parent":0,"menu_order":1,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-15","page","type-page","status-publish","hentry","author-2"],"_links":{"self":[{"href":"https:\/\/geiselmed.dartmouth.edu\/bliska\/wp-json\/wp\/v2\/pages\/15","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/geiselmed.dartmouth.edu\/bliska\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/geiselmed.dartmouth.edu\/bliska\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/geiselmed.dartmouth.edu\/bliska\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/geiselmed.dartmouth.edu\/bliska\/wp-json\/wp\/v2\/comments?post=15"}],"version-history":[{"count":6,"href":"https:\/\/geiselmed.dartmouth.edu\/bliska\/wp-json\/wp\/v2\/pages\/15\/revisions"}],"predecessor-version":[{"id":72,"href":"https:\/\/geiselmed.dartmouth.edu\/bliska\/wp-json\/wp\/v2\/pages\/15\/revisions\/72"}],"wp:attachment":[{"href":"https:\/\/geiselmed.dartmouth.edu\/bliska\/wp-json\/wp\/v2\/media?parent=15"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}