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Human islets of Langerhans express the δ C isoform of calcium/calmodulin‐dependent protein kinase II
Author(s) -
Southam Lorraine,
Ashfield Rebecca,
Cox Roger,
Lathrop Mark,
Ashcroft Stephen J.H.
Publication year - 1999
Publication title -
diabetes/metabolism research and reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.307
H-Index - 110
eISSN - 1520-7560
pISSN - 1520-7552
DOI - 10.1002/(sici)1520-7560(199907/08)15:4<243::aid-dmrr40>3.0.co;2-3
Subject(s) - gene isoform , calmodulin , calcium , protein kinase a , microbiology and biotechnology , chemistry , kinase , islet , medicine , endocrinology , biochemistry , biology , diabetes mellitus , gene
Background There is considerable evidence that calcium/calmodulin‐dependent protein kinase II (CaM kinase II) plays a key role in insulin secretion and the enzyme provides a candidate gene for Type 2 diabetes. Since several isoforms of the enzyme exist, it is essential to define which are expressed by the β ‐cell. Methods A human islet cDNA library in λ ZAPII was screened with a probe for the 5′‐end of human γ CaM kinase II. Since this region is very homologous between the different isoforms, it is expected that isoforms other than γ would be detected. From each of the six positive clones obtained, DNA was prepared and subjected to PCR using primers spanning the variable region in which the main variability of CaM kinase II isoforms resides. PCR products were purified and sequenced in both directions. The β ‐cell line MIN6 was screened for CaM kinase II δ by reverse transcriptase‐polymerase chain reaction (RT‐PCR) and by Western blotting. Results The sequences of five of the human islet PCR products indicated that the clones corresponded to the γ B isoform whose expression in human islets we have previously documented. The other PCR product, however, gave a sequence containing the variable domains II and VII characteristic of CaM kinase II δ . This sequence and the absence of other domains in this region identified the clone as CaM kinase II δ C . The expression of CaM kinase II δ in MIN6 β ‐cells was confirmed by RT‐PCR and by Western blotting. Conclusions Human islets of Langerhans express the δ C isoform of CaM kinase II. Copyright © 1999 John Wiley & Sons, Ltd.