Cellular and Molecular Neurobiology (2018) 38:1283–1292
Permanent Photodynamic Cholecystokinin 1 Receptor Activation:
Wen Yi Jiang
· Yuan Li
· Zhi Ying Li
· Zong Jie Cui
Received: 5 April 2018 / Accepted: 30 May 2018 / Published online: 4 June 2018
© Springer Science+Business Media, LLC, part of Springer Nature 2018
The G protein-coupled cholecystokinin 1 receptor (CCK1R) is activated permanently by type II photodynamic action (i.e.,
by singlet oxygen) in the freshly isolated rat pancreatic acini, in contrast to reversible activation by CCK. But how CCK1R
is photodynamically activated is not known. Therefore, in the present work, we subjected membrane proteins extracted from
isolated rat pancreatic acini to photodynamic action with photosensitiser sulphonated aluminium phthalocyanine (SALPC),
and used reducing gel electrophoresis and Western blot to detect possible changes in CCK1R oligomerization status. Photo-
dynamic action (SALPC 1 µM, light 36.7 mW cm
× 10 min) was found to convert dimeric CCK1R nearly quantitatively
to monomers. Such conversion was dependent on both irradiance (8.51–36.7 mW cm
) and irradiation time (1–20 min).
Minimum eﬀective irradiance was found to be 11.1 mW cm
(× 10 min, with SALPC 1 µM), and brief photodynamic action
(SALPC 1 µM, 36.7 mW cm
× 1 min) was eﬀective. Whilst CCK stimulation of puriﬁed membrane proteins alone had no
eﬀect on CCK1R dimer/monomer balance, sub-threshold photodynamic action (SALPC 100 nM, 36.7 mW cm
× 10 min)
plus CCK revealed a bell-shaped CCK dose response curve for CCK1R monomerization, which was remarkably similar to
the dose response curve for CCK-stimulated amylase secretion in isolated rat pancreatic acini. These two lines of evidence
together suggest that during photodynamic CCK1R activation, CCK1R is permanently monomerized, thus providing a unique
approach for permanent G protein-coupled receptor (GPCR) activation which has not been achieved before.
Keywords Cholecystokinin 1 receptor (CCK1R) · Permanent activation · Photodynamic pharmacology · G protein-coupled
receptor activated by singlet oxygen (GPCR-ABSO)
Cholecystokinin (CCK) 1 receptors (CCK1R) mediate phys-
iological functions such as exocrine pancreatic secretion,
gallbladder contraction, gastrointestinal motility (Desai et al.
2014; Ozaki et al. 2013; Dong et al. 2015), satiety and other
sensations (Ozaki et al. 2013; Broberger et al. 2001; Kac-
zynska and Szereda-Przestaszewska 2015; Li et al. 2011).
Importantly, CCK1R are expressed in hippocampus and
deﬁned extracortical sites (Nishimura et al. 2015; Ballaz
We have previously found that CCK1R is permanently
activated by type II photodynamic action with photosensitis-
ers such as sulphonated aluminium phthalocyanine (SALPC)
by generating singlet oxygen (
) at the plasma membrane
in the freshly isolated rat pancreatic acini (Cui and Kanno
1997; Cui et al. 1997; An et al. 2003; Jiang et al. 2017).
CCK1R is permanently activated also by SALPC photody-
namic action in rat pancreatic acinar tumor cell AR4-2J, and
permanently activated after ectopical expression in cell lines
by photodynamic action with SALPC and with genetically
encoded protein photosensitisers KillerRed and miniSOG
(Jiang et al. 2018). Such permanent photodynamic CCK1R
activation leads to persistent physiological-like calcium
oscillations (Cui and Kanno 1997; Cui et al. 1997; An et al.
2003; Jiang et al. 2018) and enhanced amylase secretion
with no detrimental eﬀect on cellular physiology (Matthews
and Cui 1989, 1990a, b; Cui and Matthews 1998; An et al.
2003). Although permanent photodynamic CCK1R activa-
tion is now ﬁrmly established, the detailed activation mecha-
nism is not known.
Most G protein-coupled receptors (GPCR) are known to
form dimers or oligomers in situ in living cells (Terrillon
* Zong Jie Cui
Institute of Cell Biology, Beijing Normal University,
Beijing 100875, China