4.5 Article

LL-37-induced host cell cytotoxicity depends on cellular expression of the globular C1q receptor (p33)

Journal

BIOCHEMICAL JOURNAL
Volume 473, Issue -, Pages 87-98

Publisher

PORTLAND PRESS LTD
DOI: 10.1042/BJ20150798

Keywords

anti-microbial peptide (AMP); gC1qR; host defence; innate immunity; keratinocyte; osteoblast

Funding

  1. Swedish Research Council [2003-7605, SB12-0019]
  2. Swedish Dental Society
  3. Southern Region within the Swedish Dental Association
  4. Greta and Johan Kock Foundation
  5. Swedish Foundation for Strategic Research [K2014-56X-13413-15-3]
  6. Ragnar Soderberg Foundation
  7. Knut and Alice Wallenberg Foundation [KAW 2011.0037]
  8. Alfred Osterlund Foundation
  9. Medical Faculty, Lund University

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The human host-defence peptide (HDP) LL-37 not only displays anti-microbial activity but also immune-modulating properties that trigger intracellular signalling events in host cells. Since the cytolytic activity of high LL-37 concentrations affects cell viability, the function of LL-37 requires tight regulation. Eukaryotic cells therefore benefit from protective measures to prevent harmful effects of LL-37. p33, also known as globular C1q receptor (gC1qR), is reported to act as an LL-37 antagonist by binding the peptide, thereby reducing its cytotoxic activity. In the present report, we show that high levels of endogenous p33 correlate with an increased viability in human cells treated with LL-37. Sub-cellular localization analysis showed p33 distribution at the mitochondria, the plasma membrane and in the cytosol. Strikingly, cytosolic overexpression of p33 significantly antagonized detrimental effects of LL-37 on cell fitness, whereas the reverse effect was observed by siRNA-induced down-regulation of p33. However, modulation of p33 expression had no effect on LL-37-induced plasma membrane pore forming capacity pointing to an intracellular mechanism. A scavenging function of intracellular p33 is further supported by co-immunoprecipitation experiments, showing a direct interaction between intracellular p33 and LL-37. Thus, our findings support an important role of intracellular p33 in maintaining cell viability by counteracting LL-37-induced cytotoxicity.

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