Biomedical Engineering Reference
In-Depth Information
Table 9.11.
Calcium channels and pumps of endothelial cells (Source: [
895
]). (
Part 3
)
Store-operated (SOC) and other channels. Activated VEGFR2 triggers activation of Ca
2
+
-release-
activated Ca
2
+
-channel (CRAC) channels.
Ion carriers
Features
Store-operated channels (SOC)
Ligand-gated Ca
2
+
-selective
Activation by IP
3
,ATP,
channels
and bradykinin
Smaller Ca
2
+
selectivity and
higher conductance than usual CRAC
CRAC
Ca
2
+
influx
Ryanodine receptors
Na
+
-Ca
2
+
exchanger
Ca
2
+
entry
Modulator (Ca
2
+
efflux)
Plasma membrane Ca
2
+
pump
Modulator (Ca
2
+
efflux)
Ca
2
+
efflux
Sarco(endo)plasmic reticulum
Ca
2
+
pump
Modulator of plateau phase
of Ca
2
+
influx
(SERCA3)
Mitochondrial Ca
2
+
uniporters
Modulator (Ca
2
+
efflux)
Na
+
,K
+
,andCa
2
+
transport
Mechanosensitive
Ca
2
+
-permeable
Inhibition by PKG
channels
Negative feedback by NOS3 activation
Permeability: Ca
2
+
>
Na
+
Shear stress-activated NSC
(2) non-selective cation channels (NSC);
41
and (3) Ca
2
+
-selective store-operated
channels.
42
Channels TRPC1 and TRPC6 are highly expressed in endothelial
cells, but TRPC3, TRPC4, and TRPC7 are weakly produced. Channels TRPC1,
41
Calcium influx via Ca
2
+
-permeable non-selective cation channels activated by vasoactive
agonists, depends on inositol trisphosphate. Constitutively open, non-selective Ca
2
+
-permeable
outwardly rectifying cation channels exist in both luminal and abluminal membranes of endo-
cardial endothelial cells. Superoxide-gated non-selective cation channels exist. Cyclic nucleotide-
gated NSCs bind to either cAMP or cGMP messenger.
42
Store-operated channels (SOC), or capacitative Ca
2
+
entry (CCE) channels, modulate Ca
2
+
entry
(in the cytosol). Capacitative and non-capacitative Ca
2
+
entry (NCCE) involve different types of
Ca
2
+
-permeable channels. Channel TRPC1 contributes to CCE process. Platelet activation relies
on an increase in intracellular Ca
2
+
concentration following Ca
2
+
release from intracellular Ca
2
+
stores and subsequent store-operated Ca
2
+
entry as well as Ca
2
+
entry, independent of Ca
2
+
store
depletion, through TRPC6, especially upon thrombin stimulation. Filled stores prevent Ca
2
+
influx
through store-operated Ca
2
+
channels, whereas empty stores promote influx of extracellular Ca
2
+
.
In vascular smooth myocytes, CCE channel contributes to vasoconstrictor and mitogenic effects
of vasoactive hormones. In endothelial cells, highly Ca
2
+
-selective agonist-activated channels
are gated by ATP, bradykinin, and IP
3
agents. Calcium-release-activated Ca
2
+
channel (CRAC)
pertains to the SOC set. Growth factor VEGFe activates CRAC channels.
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