Perforin evolved from a gene duplication of MPEG1, followed by a complex pattern of gene gain and loss within Euteleostomi

Abstract

BackgroundThe pore-forming protein perforin is central to the granule-exocytosis pathway used by cytotoxic lymphocytes to kill abnormal cells. Although this mechanism of killing is conserved in bony vertebrates, cytotoxic cells are present in other chordates and invertebrates, and their cytotoxic mechanism has not been elucidated. In order to understand the evolution of this pathway, here we characterize the origins and evolution of perforin.ResultsWe identified orthologs and homologs of human perforin in all but one species analysed from Euteleostomi, and present evidence for an earlier ortholog in Gnathostomata but not in more primitive chordates. In placental mammals perforin is a single copy gene, but there are multiple perforin genes in all lineages predating marsupials, except birds. Our comparisons of these many-to-one homologs of human perforin show that they mainly arose from lineage-specific gene duplications in multiple taxa, suggesting acquisition of new roles or different modes of regulation. We also present evidence that perforin arose from duplication of the ancient MPEG1 gene, and that it shares a common ancestor with the functionally related complement proteins.ConclusionsThe evolution of perforin in vertebrates involved a complex pattern of gene, as well as intron, gain and loss. The primordial perforin gene arose at least 500 million years ago, at around the time that the major histocompatibility complex-T cell receptor antigen recognition system was established. As it is absent from primitive chordates and invertebrates, cytotoxic cells from these lineages must possess a different effector molecule or cytotoxic mechanism.

Perforin-2 Restricts Growth of Chlamydia trachomatis in Macrophages

“…The broad conservation of perforin-2 among eukaryotes, coupled with evidence that perforin-1 evolved from a duplication of mpeg1 (46), is indicative of an primordial defense role for perforin-2. Likewise, coevolution of Chlamydia spp.…”

Macrophage-Expressed Perforins Mpeg1 and Mpeg1.2 Have an Anti-Bacterial Function in Zebrafish

“…While the roles of these proteins in host defence are well understood, the function of the structurally related MPEG1/perforin-2 family in macrophages remains to be fully elucidated [3,9]. In zebrafish, an mpeg1 -expressing population of macrophages develops during the first day of embryogenesis [13].…”

“…MPEG1 was first identified as a macrophage-specific gene in humans and mice, but how it contributes mechanistically to macrophage defence remains to be elucidated [3,5]. Homologs of MPEG1 are found in marine metazoans, such as the sea sponge [6], the pacific oyster [7], and the abalone shellfish [8], and evolutionary reconstruction suggests that an ancestral MPEG1 gene gave rise to the vertebrate perforin genes [9]. The expression of MPEG1 homologs in the invertebrates is upregulated by viral and bacterial infections or by exposure to bacterial lipopolysaccharides (LPS) [6,7,8].…”

Proinflammatory Caspase A Activation and an Antiviral State Are Induced by a Zebrafish Perforin after Possible Cellular and Functional Diversification from a Myeloid Ancestor

“…Contrary to what occurs in higher vertebrates, fish species have more than 1 perforin gene in their genomes. As suggested by D'Angelo et al [7], this fact could imply the existence of multiple or different functions for fish perforin genes.…”

“…The MACPF domain is also found in other molecules involved in the immune system, such as MPEG1 and complement components C6-C9. Furthermore, MPEG1, a protein produced exclusively by macrophages [6], has recently been identified as the precursor of perforin [7]. …”