© Springer International Publishing AG 2017 69
T. Angelone et al. (eds.), Chromogranins: from Cell Biology to Physiology
and Biomedicine, UNIPA Springer Series, DOI 10.1007/978-3-319-58338-9_5
Conserved Nature of the Inositol
1,4,5-Trisphosphate Receptor
and Chromogranin Coupling and Its Universal
Importance in Ca2+ Signaling of Secretory Cells
Coupling of Inositol 1,4,5-Trisphosphate
Receptor/Ca2+ Channel and Chromogranin
Seung Hyun Yoo
Abstract Secretory granules have been demonstrated to be the major inositol
1,4,5-trisphosphate (IP 3 )-sensitive intracellular Ca2+ stores in secretory cells, pri-
marily due to the presence of high concentrations of the Ca2+ storage proteins chro-
mogranins and the IP 3 receptor (IP 3 R)/Ca2+ channels in addition to 40 mM Ca2+.
Among the many extraordinary features of secretory granules is the coupling to the
IP 3 R/Ca2+ channels and the channel-modulatory roles of chromogranins, increasing
the open probability and the mean open time of the channels multiple-fold.
Particularly noteworthy is that most conserved regions of chromogranins A (CGA)
and B (CGB) and of the IP 3 Rs, i.e., the near amino (N)-terminal region of chromo-
granins A and B and the last intraluminal loop (L3-2 loop) of the IP 3 Rs, participate
in the coupling. Given that the two regions which participate in the coupling are
highly conserved in the biokingdom, the coupling between chromogranins and the
IP 3 R/Ca2+ channels appears to be a very ancient molecular design forming the IP 3 -
dependent Ca2+ signaling systems of organisms. Although the coupling is uncovered
in secretory cells, similar molecular arrangements which involve the IP 3 R/Ca2+
channels and some type of Ca2+ storage and/or Ca2+ channel-modulatory proteins
that are functionally equivalent to chromogranins in secretory cells will also exist in
nonsecretory cells.
S.H. Yoo (*)
Gran Med Inc., Get Pearl Tower 304, Get Pearl Ro 12, Yeonsu Gu,
Incheon 21999, South Korea
e-mail: [email protected]