Caveolae localization and caveolin expressions in Schwann cells of mature rat spinal nerves

Immunofluorescence-Based Analysis of Caveolin-3 in the Diagnostic Management of Neuromuscular Diseases

Immunohistochemistry- and/or immunofluorescence-based analysis of muscular proteins represents a standard procedure in the diagnostic management of patients suffering from neuromuscular diseases such as "Caveolinopathies" which are caused by mutations in the CAV3 gene encoding for caveolin-3. Human caveolin-3 is a 151 amino acid sized transmembrane protein localized within caveolae, predominantly expressed in cardiac and skeletal muscle cells and involved in a diversity of cellular functions crucial for muscle cell homeostasis. Loss of caveolin-3 protein abundance is indicative for the presence of pathogenic mutations within the corresponding gene and thus for the diagnosis of "Caveolinopathies." Moreover, description of abnormal immunoreactivity findings for the caveolin-3 protein is increasing in the context of other neuromuscular diseases suggesting that profound knowledge of abnormal caveolin-3-expression and/or distribution findings can be decisive also for the diagnosis of other neurological diseases as well as for a better understanding of the biology of the protein. Here, we summarize the current knowledge about the caveolin-3, report on a protocol for immunofluorescence-based analysis of the protein in the diagnostic workup of neuromuscular patients-also considering problems encountered-and confirm as well as summarize already published abnormal histological findings in muscular pathologies beyond "Caveolinopathies."

Distribution of caveolin in the muscle spindles of human skeletal muscle

The aim of the present study was to demonstrate the location of the different members of the caveolin (cav) family in human muscle spindles. Twenty spindles of three human muscles (vastus medialis, ischiocavernosus, bulbospongiosus) from 12 cadavers were immunohistochemically stained for cav-1, cav-2, and cav-3, and the equatorial and polar regions evaluated. All layers of the outer and inner spindle capsule and all blood vessels within the spindle stained for cav-1 and cav-2. In the muscle spindle, intrafusal muscle fibres stained selectively for cav-3, but with a patchy appearance. Caveolinopathies may therefore also include changes in muscle spindle function.

Differential cell-specific location of Cav-1 and Ca(2+)-ATPase in terminal Schwann cells and mechanoreceptive Ruffini endings in the periodontal ligament of the rat incisor

Caveolae are involved in clathrin-independent endocytosis, transcytosis, signal transduction, and tumor suppression - all of which depend on their main constituent protein caveolin families. The periodontal Ruffini ending has been reported to develop a caveola-like structure on the cell membrane of both the axon terminals and Schwann sheaths, suggesting the existence of an axon-Schwann cell interaction in the periodontal Ruffini endings. However, little information is available concerning the functional significance of these caveolae. The present study was undertaken to examine the immunolocalization of caveolin-1, -3 (Cav-1, Cav-3) and Ca(2+)-ATPase in the periodontal Ruffini endings of the rat incisor. Decalcified sections of the upper jaws were processed for immunocytochemistry at the levels of light and electron microscopy. Some immunostained sections were treated with histochemistry for nonspecific cholinesterase (nChE) activity. Observations showed the periodontal Ruffini endings were immunopositive for Cav-1, but not Cav-3. Immunoreactive products for Cav-1 were confined to caveola-like structures in the cell membranes of the cytoplasmic extensions and cell bodies of the terminal Schwann cells associated with the periodontal Ruffini endings. However, the axonal membranes of the terminals did not express any Cav-1 immunoreaction. Double staining with Ca(2+)-ATPase and either protein gene product 9.5 (PGP 9.5) or S-100 protein disclosed the co-localization of immunoreactions in the axonal branches of the periodontal Ruffini endings, but not in the terminal Schwann cells. As Ca(2+) plays an important role in mechanotransduction, these characteristic immunolocalizations show Cav-1/Ca(2+)-ATPase might be involved in the quick elimination of intracellular Ca(2+) in mechanotransduction.

Expression of caveolin-3 immunoreactivities in the developing sciatic nerve of the rat

Caveolae are formed by the caveolin (CAV) family of proteins, CAV-1, -2, and -3. CAV-1 and -2 are co expressed in many cell types, whereas CAV-3 is muscle-specific and mutation of the CAV-3 gene causes muscular dystrophy. CAV-3 has also been detected in brain astroglial cells and in peripheral nerves along with CAV-1. Therefore, we sought to determine whether CAV-3 protein is expressed in developing peripheral nerves by using immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). We found that CAV-3 immunoreactivities (IRs) were Localized in the myelin sheath during peripheral nerve development. CAV-3 IRs were intense during the early postnatal stage, but decreased as the peripheral nerves matured at postnatal weeks 3-5. CAV-3 mRNA expression was also markedly decreased during postnatal development. Because the expression pattern of CAV-3 IRs was opposite that of CAV-1 IRs. CAV-1 and -3 might be involved in different phases of peripheral nerve myelination and play complementary roles in myelin maturation and peripheral nerve development.

Caveolins in glial cell model systems: from detection to significance

Glial cells prevail in number and in diversity of cellular phenotypes in the nervous system. They have also gained prominence due to their multiple physiological and pathophysiological roles. Our current knowledge of the asymmetry and heterogeneity of the plasma membrane demands an in depth analysis of the diverse array of membrane microdomains postulated to exist in the context of glial cells. This review focuses and analyzes the studies reported to date on the detection of caveolae membrane rafts and the caveolin family members in glial cell model systems, the conditions leading to changes in their level of expression, and their functional and clinical significance. Outstanding in this work emerge the ubiquitous expression of caveolins, including the typically regarded 'muscle-specific' cav3, in diverse glial cell model systems, their participation in reactive astrogliosis, cancer, and their key relevance to calcium signaling. The knowledge obtained to date demands incorporation of the caveolins and caveolae membrane rafts in our current models on the role of glial cells in heath and neurological disease.

Neurological abnormalities in caveolin-1 knock out mice

Caveolin-1 is the defining structural protein in caveolar vesicles, which regulate signal transduction and cholesterol trafficking in cells. In the brain, cav-1 is highly expressed in neurons and glia, but its function in those cell types is unclear. Mice deficient in cav-1 (CavKO) have been developed to test functional roles for cav-1 in various tissues. However, neurological phenotypes associated with loss of cav-1 in mice have not been evaluated. Here, we report the results of motor and behavioral testing of CavKO mice. We find that mice deficient in cav-1 have reduced brain weight and display a number of motor and behavioral abnormalities. CavKO mice develop neurological phenotypes including clasping, abnormal spinning, muscle weakness, reduced activity, and gait abnormalities. These data suggest that cav-1 is involved in maintaining cortico-striato-pallido-thalamo-pontine pathways associated with motor control.