LL-37-induced host cell cytotoxicity depends on cellular expression of the globular C1q receptor (p33).
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.
Department of Experimental Medical Science, Lund University, BMC D12, SE-22184 Lund, Sweden.
Daniel
D
Svensson
Department of Clinical Sciences, Division of Infection Medicine, Lund University, BMC C14, SE-22184 Lund, Sweden.
Laura
L
Wilk
Department of Clinical Sciences, Division of Infection Medicine, Lund University, BMC C14, SE-22184 Lund, Sweden.
Matthias
M
Mörgelin
Department of Clinical Sciences, Division of Infection Medicine, Lund University, BMC C14, SE-22184 Lund, Sweden.
Heiko
H
Herwald
Department of Experimental Medical Science, Lund University, BMC D12, SE-22184 Lund, Sweden bengt-olof.nilsson@med.lu.se.
Bengt-Olof
BO
Nilsson
D000293:Adolescent; D023181:Antimicrobial Cationic Peptides / Q000633:toxicity*; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism*; D002478:Cells, Cultured; D003603:Cytotoxins / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D011951:Receptors, Complement / Q000096:biosynthesis* / Q000235:genetics; D054804:Cathelicidins
D023181:Antimicrobial Cationic Peptides; D003603:Cytotoxins; D008562:Membrane Glycoproteins; D011951:Receptors, Complement; C032402:complement 1q receptor; D054804:Cathelicidins
anti-microbial peptide (AMP); gC1qR; host defence; innate immunity; keratinocyte; osteoblast