Age-dependent expression of protein kinase C isoforms in rat islets
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Published on: January 7, 2013
1Department of Anatomy and Cell Biology, School of Medicine, East Carolina University, Greenville, North Carolina 27858-4354.
Insights
Protein Kinase C (PKC) isoforms are present in neonatal rat islets, with specific types appearing during early development. This emergence of PKC enzymes correlates with the maturation of insulin secretion in newborns.
Area of Science:
- Endocrinology
- Molecular Biology
- Developmental Biology
Background:
- The biphasic insulin secretory response develops postnatally, indicating critical maturation of stimulus-secretion coupling.
- Protein Kinase C (PKC) is implicated in cellular signaling pathways, including hormone secretion.
Purpose of the Study:
- To investigate the presence and cell-specific localization of PKC isoenzymes in rat pancreatic islets during development.
- To determine the developmental expression pattern of PKC isoforms and its potential link to neonatal insulin secretion.
Main Methods:
- Western-blot analysis of pancreatic islet extracts from fetal, neonatal, and adult rats.
- Immunocytochemistry to detect the localization of PKC isoenzymes within different islet cell types.
Main Results:
- PKC-alpha, -gamma, and -epsilon isoforms were detected in adult and neonatal rat islets.
- In adult islets, PKC-alpha localized to beta-cells, PKC-gamma to alpha-cells, and PKC-epsilon to delta-cells and vasculature.
- PKC-alpha and -gamma expression was significantly reduced in neonatal islets compared to adults, and absent in fetal islets.
Conclusions:
- Specific PKC isoenzymes are differentially expressed in distinct islet cell types, suggesting roles in regulating specific hormone secretion.
- The appearance of PKC-alpha and -gamma during the early neonatal period coincides with the development of biphasic insulin release.
- Age-dependent expression of PKC isoforms is likely crucial for the maturation of pancreatic islet function and glucose homeostasis.
Abstract:
The appearance of the biphasic insulin secretory response several days after birth suggests that maturation of a critical step in stimulus-secretion coupling occurs during the early neonatal period. To clarify the role of protein kinase C (PKC) during this time, we examined the pancreatic islets of adult, 3-day neonatal, and 19-day fetal rats for the presence of different PKC isoenzymes. Western-blot analysis of islet extracts showed the presence of PKC isoforms in both adult and neonatal tissues. Immunocytochemistry of adult islets revealed a differential expression in islet cell types. PKC-alpha was found only in beta-cells, PKC-gamma in alpha-cells, and PKC-epsilon in delta-cells and vascular walls. Immunoreactivity for PKC-beta was not detected in any cell type. All three isoenzymes were also present in neonatal islets; however, in contrast to adult tissue, immunoreactivity for either PKC-alpha or PKC-gamma was present in relatively few cells. There was no apparent immunoreactivity for PKC-alpha or PKC-gamma in fetal islets, although these tissues contained strong staining for insulin and glucagon. These data show that three of the PKC isoforms are restricted to a particular islet cell type, where they may play a unique role in the secretion of a specific hormone. Moreover, our results demonstrate that these enzymes, especially PKC-alpha, appear during the early neonatal period. This age-dependent expression may be linked to the development of the biphasic insulin release response.
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