Asymmetric inheritance of mTORC1 kinase activity during division dictates CD8(+) T cell differentiation.
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ABSTRACT:
SUBMITTER: Pollizzi KN
PROVIDER: S-EPMC4873361 | biostudies-literature | 2016 Jun
REPOSITORIES: biostudies-literature
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Project description:During an immune response against a microbial pathogen, activated naive T lymphocytes give rise to effector cells that provide acute host defense and memory cells that provide long-lived immunity. It has been shown that T lymphocytes can undergo asymmetric division, enabling the daughter cells to inherit unequal amounts of fate-determining proteins and thereby acquire distinct fates from their inception. In this study, we show that the absence of the atypical protein kinase C (PKC) isoforms, PKCζ and PKCλ/ι, disrupts asymmetric CD8(+) T lymphocyte division. These alterations were associated with aberrant acquisition of a pre-effector transcriptional program, detected by single-cell gene expression analyses, in lymphocytes that had undergone their first division in vivo and enhanced differentiation toward effector fates at the expense of memory fates. Together, these results demonstrate a role for atypical PKC in regulating asymmetric division and the specification of divergent CD8(+) T lymphocyte fates early during an immune response.
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Project description:Asymmetric cell division (ACD) is believed to be a physiological event that occurs during development and tissue homeostasis in a large variety of organisms. ACD produces two unequal daughter cells, one of which resembles a multipotent stem and/or progenitor cell, whereas the other has potential for differentiation. Although recent studies have shown that the balance between self-renewal and differentiation potentials is precisely controlled and that alterations in the balance may lead to tumorigenesis in Drosophila neuroblasts, it is largely unknown whether human cancer cells directly show ACD in an evolutionarily conserved manner. Here, we show that the conserved polarity/spindle protein NuMA is preferentially localized to one side of the cell cortex during cell division, generating unequal inheritance of fate-altering molecules in human neuroblastoma cell lines. We also show that the cells with a single copy of MYCN showed significantly higher percentages of ACD than those with MYCN amplification. Moreover, suppression of MYCN in MYCN-amplified cells caused ACD, whereas expression of MYCN in MYCN-nonamplified cells enhanced symmetric cell division. Furthermore, we demonstrate that centrosome inheritance follows a definite rule in ACD: The daughter centrosome with younger mother centriole is inherited to the daughter cell with NuMA preferentially localized to the cell cortex, whereas the mother centrosome with the older mother centriole migrates to the other daughter cell. Thus, the mechanisms of cell division of ACD or symmetric cell division and centrosome inheritance are recapitulated in human cancer cells, and these findings may facilitate studies on cancer stem cells.
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Project description:Naïve CD8(+) T lymphocytes responding to microbial pathogens give rise to effector T cells that provide acute defense and memory T cells that provide long-lived immunity. Upon activation, CD8(+) T lymphocytes can undergo asymmetric division, unequally distributing factors to the nascent daughter cells that influence their eventual fate towards the effector or memory lineages. Individual loss of either atypical protein kinase C (aPKC) isoform, PKCζ or PKCλ/ι, partially impairs asymmetric divisions and increases CD8(+) T lymphocyte differentiation toward a long-lived effector fate at the expense of memory T cell formation. Here, we show that deletion of both aPKC isoforms resulted in a deficit in asymmetric divisions, increasing the proportion of daughter cells that inherit high amounts of effector fate-associated molecules, IL-2Rα, T-bet, IFNγR, and interferon regulatory factor 4 (IRF4). However, unlike CD8(+) T cells deficient in only one aPKC isoform, complete loss of aPKC unexpectedly increased CD8(+) T cell differentiation toward a short-lived, terminal effector fate, as evidenced by increased rates of apoptosis and decreased expression of Eomes and Bcl2 early during the immune response. Together, these results provide evidence for an important role for asymmetric division in CD8(+) T lymphocyte fate specification by regulating the balance between effector and memory precursors at the initiation of the adaptive immune response.
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