Characterization of serine/threonine protein phosphatases in RINm5F insulinoma cells

Åke Sjöhom; Richard E. Honkanen; Per Olof Berggren

doi:10.1007/BF01150479

Characterization of serine/threonine protein phosphatases in RINm5F insulinoma cells

Åke Sjöhom, Richard E. Honkanen, Per Olof Berggren

Surgery

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25 Scopus citations

Abstract

This study investigates the occurrence and regulation of serine/threonine protein phosphatases (PPases) in insulin-secreting RINm5F insulinoma cells. PPases types 1 and 2A were identified in crude RINm5F cell homogenates by both enzymatic assay and Western blot analysis. We then characterized and compared the inhibitory actions of several compounds isolated from cyanobacteria, marine dinoflagellates and marine sponges, (viz. okadaic acid, microcystin-LR, calyculin-A and nodularin) cation-independent PPase activities in RINm5F cell homogenates. It was found that okadaic acid was the least potent inhibitor (IC₅₀≈10^-9M, IC₁₀₀≈10^-6M), while the other compounds exhibited IC₅₀ values of ≈5·10^-10 M and IC₁₀₀≈ 5·10^-9 M. The findings indicate that the inhibitory substances employed in this study may be used pharmacologically to investigate the role of serine/threonine PPases in RINm5F cell insulin secretion, a process that is likely to be regulated to a major extent by protein phosphorylation.

Original language	English (US)
Pages (from-to)	349-358
Number of pages	10
Journal	Bioscience reports
Volume	13
Issue number	6
DOIs	https://doi.org/10.1007/BF01150479
State	Published - Dec 1993

Keywords

insulin secretion
insulinoma
okadaic acid
protein phosphatase

ASJC Scopus subject areas

Cell Biology
Biochemistry, Genetics and Molecular Biology(all)

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10.1007/BF01150479

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title = "Characterization of serine/threonine protein phosphatases in RINm5F insulinoma cells",

abstract = "This study investigates the occurrence and regulation of serine/threonine protein phosphatases (PPases) in insulin-secreting RINm5F insulinoma cells. PPases types 1 and 2A were identified in crude RINm5F cell homogenates by both enzymatic assay and Western blot analysis. We then characterized and compared the inhibitory actions of several compounds isolated from cyanobacteria, marine dinoflagellates and marine sponges, (viz. okadaic acid, microcystin-LR, calyculin-A and nodularin) cation-independent PPase activities in RINm5F cell homogenates. It was found that okadaic acid was the least potent inhibitor (IC50≈10-9M, IC100≈10-6M), while the other compounds exhibited IC50 values of ≈5·10-10 M and IC100≈ 5·10-9 M. The findings indicate that the inhibitory substances employed in this study may be used pharmacologically to investigate the role of serine/threonine PPases in RINm5F cell insulin secretion, a process that is likely to be regulated to a major extent by protein phosphorylation.",

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AU - Honkanen, Richard E.

AU - Berggren, Per Olof

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N2 - This study investigates the occurrence and regulation of serine/threonine protein phosphatases (PPases) in insulin-secreting RINm5F insulinoma cells. PPases types 1 and 2A were identified in crude RINm5F cell homogenates by both enzymatic assay and Western blot analysis. We then characterized and compared the inhibitory actions of several compounds isolated from cyanobacteria, marine dinoflagellates and marine sponges, (viz. okadaic acid, microcystin-LR, calyculin-A and nodularin) cation-independent PPase activities in RINm5F cell homogenates. It was found that okadaic acid was the least potent inhibitor (IC50≈10-9M, IC100≈10-6M), while the other compounds exhibited IC50 values of ≈5·10-10 M and IC100≈ 5·10-9 M. The findings indicate that the inhibitory substances employed in this study may be used pharmacologically to investigate the role of serine/threonine PPases in RINm5F cell insulin secretion, a process that is likely to be regulated to a major extent by protein phosphorylation.

AB - This study investigates the occurrence and regulation of serine/threonine protein phosphatases (PPases) in insulin-secreting RINm5F insulinoma cells. PPases types 1 and 2A were identified in crude RINm5F cell homogenates by both enzymatic assay and Western blot analysis. We then characterized and compared the inhibitory actions of several compounds isolated from cyanobacteria, marine dinoflagellates and marine sponges, (viz. okadaic acid, microcystin-LR, calyculin-A and nodularin) cation-independent PPase activities in RINm5F cell homogenates. It was found that okadaic acid was the least potent inhibitor (IC50≈10-9M, IC100≈10-6M), while the other compounds exhibited IC50 values of ≈5·10-10 M and IC100≈ 5·10-9 M. The findings indicate that the inhibitory substances employed in this study may be used pharmacologically to investigate the role of serine/threonine PPases in RINm5F cell insulin secretion, a process that is likely to be regulated to a major extent by protein phosphorylation.

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