Localization of protein kinase C theta immunoreactivity to interstitial cells of Cajal in guinea‐pig gastrointestinal tract

Abstract

In the gastrointestinal tract, interstitial cells of Cajal (ICC) are located between nerve fibres and muscle cells and have a role in neuromuscular transmission and muscle contractility. Protein kinase C (PKC) is involved in modulation of muscle contractility by neurotransmitters, but it is not known if PKC has a role in ICC. There are 11 different PKC isoforms. The presence of PKC isoforms in ICC in guinea-pig gastrointestinal tract was examined using fluorescence immunohistochemistry and confocal microscopy. Segments of guinea-pig stomach, duodenum, ileum, proximal and distal colon were fixed in zambonis fixative. Frozen sections and wholemounts were incubated with anti-PKC antibodies (alpha, beta, delta, epsilon, gamma, iota, lambda, mu, theta) followed by fluorescent secondary antibody. Only PKC theta (theta) immunoreactivity was found in ICC. None of the other PKC isoforms (alpha, beta, delta, epsilon, gamma, iota, lambda, mu) localized to the ICC. PKC theta immunoreactivity was prominent in ICC located between the circular and longitudinal muscle layers (ICC-MY) in all regions except stomach and within the circular muscle (ICC-IM) in the large intestine. PKC theta was not present in ICC in the deep muscular plexus in either duodenum or ileum. PKC theta immunoreactivity was present in the cell body and proximal processes of the ICC. The cells containing PKC theta also contained cKit confirming the cells were ICC. ICC-MY in the ileum also contained the neurokinin (NK) 1 receptor. In conclusion, PKC theta is present in pacemaker ICC, but its function is not yet known. Functional studies will be needed to determine the role of this kinase in ICC. Knowing the second messenger cascades and being able to manipulate subpopulations of ICC will add to our understanding of the molecular and cell biology of ICC networks within the gastrointestinal tract and may ultimately help in understanding the aetiology of some gastrointestinal motor pathologies.

Selective labeling and isolation of functional classes of interstitial cells of Cajal of human and murine small intestine

“…For example, previous studies have shown that ICC express a variety of receptors, including peptide receptors, such as neurokinin (19,25,32,46), somatostatin (41) and VIP receptors (7), M 2 and M 3 muscarinic receptors (7), and nucleotide receptors (5). Expression of intracellular signaling intermediates such as protein kinases (30,40) and cGMP (38,55) is also consistent with a role for ICC-IM in mediating neuroeffector functions. Moreover, ICC-IM may also amplify the efferent neuronal signals by producing intercellular signaling molecules, such as nitric oxide (33,45), CO (27), and prostaglandins (31).…”

“…On the other hand, ICC that mediate communication between enteric motor neurons and smooth muscle cells (i.e., ICC-IM) are closely associated with neural processes and lie within muscle bundles (34,35,53). However, despite differences in morphology, distribution, and function, members of ICC classes share many common characteristics including some ultrastructural features and expression of Kit, neurotransmitter receptors, signaling intermediates, and ion channels (7,25,27,30,40,45). The division of labor concept is further blurred by recent findings suggesting that ICC-IM may generate pacemaker activity in the guinea pig and murine gastric antrum (8,13,14).…”

Protein kinase C-θ regulates KIT expression and proliferation in gastrointestinal stromal tumors

“…It is particularly intriguing that PKCy regulates KIT expression in GIST, given that PKCy and KIT have restricted ranges of expression in human cells, and are both coexpressed at unusually high levels in interstitial cells of Cajal, which are non-neoplastic counterparts of GIST (Southwell, 2003). Although the mechanisms by which PKCy regulates KIT gene expression remain to be determined, there is precedent-in T cells-for PKCy modulation of transcriptional regulators.…”

Ménétrier disease and gastrointestinal stromal tumors: hyperproliferative disorders of the stomach

“…GISTs have features in common with the myenteric plexus subtype of ICCs that are found in the stomach and intestines, including frequent expression of CD34, embryonic smooth muscle myosin heavy chain, the intermediate filament nestin, and PKC-θ (72)(73)(74)(75)(76)(77)(78). Myenteric plexus ICCs fail to develop in mice that lack expression of KIT or its ligand, SCF, indicating that the SCF-KIT axis is essential to the development of these cells (79,80).…”