Effect of ENV59-GP3 peptide on calcium influx following
Ca2+ depletion in THP-1 cells
To measure the effects of ENV59-GP3 peptide and NS6180 blocker on
calcium flux, THP-1 cells were loaded with the calcium sensitive dye
Fluo-4 and incubated with either ENV59-GP3 peptide or NS6180 blocker,
and/or with the calcium store depleting agent Thapsigargin, an inhibitor
of the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA)
[25] (Figure 4A). Similarly, both ENV59-GP3 peptide and NS6180
reduced the influx-mediated Ca2+ accumulation induced
by Thapsigargin. In comparison, an immune suppressive peptide isolated
from the influenza hemagglutinin (Flu ISU) which has a similar
immunosuppressive phenotype to ENV59-GP3 [21], but interacts with
and inhibits dimerization of the stimulator of interferon genes (STING)
[21] did not have a significant effect in the
[Ca2+]I in this assay. Thus, the
ENV59-GP3 peptide’s biological activity is more similar to the
KCa3.1 inhibitor than it is to an influenza
virus-derived immunosuppressive peptide.