Manganese-stimulated phosphorylation of a rat pancreatic protein: identity with elongation factor 2

Knight, Simon A. B.; Kohr, William J.; Korc, Murray

doi:10.1016/0167-4889(91)90157-s

Cited by 6 publications

(2 citation statements)

References 44 publications

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“…Metabolic labeling of isolated pancreatic acini with [ 32 P]orthophosphate followed by phosphoprotein analysis using twodimensional gel electrophoresis allows the distinction of up to 300 phosphoproteins, ϳ30 of which have been shown to be acutely regulated by secretagogues (36). A number of these regulated phosphoproteins have been identified in acini by protein purification and use of specific antibodies (10,13,14,18,36). A typical phosphoprotein pattern from 32 P-labeled acini is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Previous studies aimed at identifying acinar cell regulatory proteins that respond to secretagogue stimulation have utilized a proteomic approach of metabolically labeling cells with [ 32 P]orthophosphate, followed by protein separation using one-and two-dimensional electrophoresis (3,4,8,26,36). This method has led to the identification of a number of key regulatory proteins that mediate acinar cell protein translation (2,18), actin cytoskeletal dynamics (10,21), and membrane trafficking events necessary for acinar secretion (13,24,25). Additionally, this strategy was used to isolate a novel physiological substrate to the Ca 2ϩcalmodulin-regulated protein phosphatase calcineurin (also known as PP2B) termed Ca 2ϩ -regulated heatstable protein of 24 kDa (CRHSP-24) (11,14).…”

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confidence: 99%

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CRHSP-24 phosphorylation is regulated by multiple signaling pathways in pancreatic acinar cells

Schäfer¹,

Steffen²,

Krzykowski³

et al. 2003

American Journal of Physiology-Gastrointestinal and Liver Physi

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Ca2+-regulated heat-stable protein of 24 kDa (CRHSP-24) is a serine phosphoprotein originally identified as a physiological substrate for the Ca2+-calmodulin regulated protein phosphatase calcineurin (PP2B). CRHSP-24 is a paralog of the brain-specific mRNA-binding protein PIPPin and was recently shown to interact with the STYX/dead phosphatase protein in developing spermatids (Wishart MJ and Dixon JE. Proc Natl Acad Sci USA 99: 2112-2117, 2002). Investigation of the effects of phorbol ester (12-o-tetradecanoylphorbol-13-acetate; TPA) and cAMP analogs in 32P-labeled pancreatic acini revealed that these agents acutely dephosphorylated CRHSP-24 by a Ca2+-independent mechanism. Indeed, cAMP- and TPA-mediated dephosphorylation of CRHSP-24 was fully inhibited by the PP1/PP2A inhibitor calyculin A, indicating that the protein is regulated by an additional phosphatase other than PP2B. Supporting this, CRHSP-24 dephosphorylation in response to the Ca2+-mobilizing hormone cholecystokinin was differentially inhibited by calyculin A and the PP2B-selective inhibitor cyclosporin A. Stimulation of acini with secretin, a secretagogue that signals through the cAMP pathway in acini, induced CRHSP-24 dephosphorylation in a concentration-dependent manner. Isoelectric focusing and immunoblotting indicated that elevated cellular Ca2+ dephosphorylated CRHSP-24 on at least three serine sites, whereas cAMP and TPA partially dephosphorylated the protein on at least two sites. The cAMP-mediated dephosphorylation of CRHSP-24 was inhibited by low concentrations of okadaic acid (10 nM) and fostriecin (1 microM), suggesting that CRHSP-24 is regulated by PP2A or PP4. Collectively, these data indicate that CRHSP-24 is regulated by diverse and physiologically relevant signaling pathways in acinar cells, including Ca2+, cAMP, and diacylglycerol.

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