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Endoplasmic Reticulum (ER) is the largest intracellular Ca 2+ store. On the membrane of the ER, there are calcium release components such as inositol 1, 4, 5 trisphosphate receptor (IP 3 R), and the calcium pumps like SR/ER Ca 2+ ATPases (SERCAs). We injected caged-IP 3 together with the fluorescent Ca 2+ indicator into the oocytes. Upon UV stimulation, activated IP 3 binds to IP 3 R and releases Ca 2+ from the ER into the cytosol. Subsequently the closure of IP 3 R and activation of SERCAs takes the cytosolic Ca 2+ back into the ER stores. We recorded the changes of intracellular Ca 2+ signals by confocal microscopy. The movie shows the different intracellular calcium responses induced by UV-uncaging of caged IP 3 in Xenopus oocytes overexpressing polycystin-2 and the water injected control.
 
Image Above: In 1992, Dr. Guggino and Dr. Peter Agre (Science 256:385-387, 1992) defined the function of the first water channel protein; research that subsequently led to Dr. Agre winning the Nobel Prize in Chemistry. Link to Publication: Preston GM, Jung JS, Guggino WB, Agre P. The mercury-sensitive residue at cysteine 189 in the CHIP28 water channel.J Biol Chem. 1993 Jan 5;268(1):17-20. PMID: 7677994 [PubMed - indexed for MEDLINE
   
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