α, βI, βII, δ, and ε Protein Kinase C Isoforms and Compound Activity in the Sciatic Nerve of Normal and Diabetic Rats

Authors

  • Isabelle Borghini,

    1. Division de Biochimie Clinique et de Diabétologie Expérimentale, Département de Médecine, Centre Médical Universitaire, Geneva, Switzerland, and
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  • Aldonza Ania-Lahuerta,

    1. Division de Biochimie Clinique et de Diabétologie Expérimentale, Département de Médecine, Centre Médical Universitaire, Geneva, Switzerland, and
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  • Romano Regazzi,

    1. Division de Biochimie Clinique et de Diabétologie Expérimentale, Département de Médecine, Centre Médical Universitaire, Geneva, Switzerland, and
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  • Giovanna Ferrari,

    1. Fidia Research Laboratories, Abano Terme, Italy
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  • Asllan Gjinovci,

    1. Division de Biochimie Clinique et de Diabétologie Expérimentale, Département de Médecine, Centre Médical Universitaire, Geneva, Switzerland, and
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  • Claes B. Wollheim,

    1. Division de Biochimie Clinique et de Diabétologie Expérimentale, Département de Médecine, Centre Médical Universitaire, Geneva, Switzerland, and
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  • William-F. Pralong

    Corresponding author
    1. Division de Biochimie Clinique et de Diabétologie Expérimentale, Département de Médecine, Centre Médical Universitaire, Geneva, Switzerland, and
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Address correspondence and reprint requests to Dr. W.-F. Pralong at Division de Biochimie Clinique et de Diabétologie Expérimentale, Département de Médecine, Centre Médical Universitaire, Case Postale, 1211 Genève 4, Switzerland.

Abstract

Abstract: Defective protein kinase C (PKC) has been implicated in impaired Na+,K+-ATPase activity in the sciatic nerve of streptozotocin-induced diabetic rats. In the present study, α, βI, βII, γ, δ, and ε isoform-specific antibodies were used in parallel to the measurement of compound PKC activity for the characterization of PKC distribution and isoform expression in sciatic nerves of normal and diabetic rats. To distinguish isoform expression between the axonal and glial compartments, PKC isoforms were evaluated in nerves subjected to Wallerian degeneration and in a pure primary Schwann cell culture. α, βI, βII, δ, and ε but no γ isoforms were detected in sciatic nerve. Similar immunoreactivity was observed in degenerated nerves 3–4 days after transection except for diminished βI and ε species; in Schwann cell cultures, only α, βII, δ, and ε were detected. In normal nerves, two-thirds of PKC compound activity was found in the cytosol and 50% of total enzyme activity translocated to the Na+,K+-ATPase-enriched membrane fraction with phorbol myristate acetate. Similar redistribution patterns were observed for the immunoreactivity of all isoforms with the exception of δ, which did not translocate to the membrane with phorbol myristate acetate. No abnormality in compound PKC activity, in the immunoreactive intensity, or in the distribution of PKC isoforms could be detected in rat sciatic nerve after 6–12 weeks of diabetes. Thus, defective activation rather than decreased intrinsic PKC activity may occur in diabetic neuropathy.

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