Immunolocalization of different forms of neural cell adhesion molecule (NCAM) in rat taste buds

Abstract

Taste buds consist of approximately 100 taste cells, including three morphological types of short receptor cells which synapse on the peripheral gustatory nerves. Some of the receptor cells produce neural cell adhesion molecule (NCAM), which may play a role in formation of specific connections in this system. Antibodies directed against different forms of NCAM were utilized in an attempt to define not only the distribution, but also the type of NCAM within taste buds. Within each taste bud approximately 10% of the taste cells exhibit abundant immunoreactivity for 180 kD (ld) or 140 kD (sd) forms of NCAM (i.e., those with an intracellular domain) along virtually the entire surface of the cell. Ultrastructural analysis reveals that these abundantly immunoreactive taste cells are of the intermediate morphological type, although not all of the intermediate taste cells within any bud are immunoreactive. In addition, the ultrastructural studies show that punctate (ld/sd) NCAM-immunoreactivity occurs on the membranes of taste cells and nerve fibers throughout each taste bud. The embryonic form of NCAM (E-NCAM), rich in polysialic acid residues, is present only in association with nerve fibers and other unidentified elongate, thin profiles of a few taste buds. The nerve plexus beneath the gustatory epithelium is also rich in NCAM-immunoreactivity. These fibers occasionally reveal immunoreactivity indicative of only the 120 kD (ssd) form of NCAM, typical of glial cells.

Targeted Taste Cell-specific Overexpression of Brain-derived Neurotrophic Factor in Adult Taste Buds Elevates Phosphorylated TrkB Protein Levels in Taste Cells, Increases Taste Bud Size, and Promotes Gustatory Innervation

“…NCAM-positive cells normally constitute only ϳ10% of the cells in mature taste buds (20). There was a clear increase in the number of NCAM-positive cells in the taste buds of the transgenic mice, as also indicated by the significant increase in the NCAM gene expression in circumvallate taste epithelia.…”

“…Type III cells respond to sour taste and carbonation (18,19) and have synaptic contacts with the gustatory nerve fibers. They express neural cell adhesion molecule (NCAM) 2 (20) as well as the synaptic membrane protein SNAP25 (21). Although both type II and III cells express BDNF, BDNF is expressed by a larger number of type III cells (22).…”

Espin cytoskeletal proteins in the sensory cells of rodent taste buds

“…Unfortunately, none of them, except for the recently described synaptobrevin-2 (Pumplin & Getschman, 2000;Yang et al, 2004), encompasses the entire population of type II and type III cells (Nelson & Finger, 1993;Pumplin et al, 1999;Yang et al, 2000;Clapp et al, 2001Clapp et al, , 2004Ueda et al, 2003;Yee et al, 2001Yee et al, , 2003Takeda et al, 2004). We chose to examine the colocalization of espin with inositol 1,4,5-trisphosphate receptor type III (IP 3 R 3 ), α-gustducin and neuronal protein gene product 9.5 (PGP9.5), as they are commonly used markers that are relatively broadly distributed throughout the cytoplasmic compartment, and their immunolabeling proved to be highly reproducible and not adversely affected by antigen-retrieval procedure needed to better reveal cytoplasmic espin.…”

Modulation of Taste Responsiveness by Angiotensin II

“…Gα-gustducin (McLaughlin et al, 1992), phospholipase C β2 (PLCβ2) (Miyoshi et al, 2001), inositol 1,4,5-trisphosphate receptor type 3 (IP3R3) (Clapp et al, 2001) and Trpm5 (Pérez et al, 2002, Talavera et al, 2005 , Horio et al, 2011 and synaptic membrane proteins such as synaptosomal-associated protein 25 (SNAP25) (Yang et al, 2000, Clapp et al, 2006, protein gene product 9.5 (PGP9.5) (Iwanaga et al, 1992), glutamic acid decarboxylase 67 (GAD67) (Tamamaki et al, 2003), and neural cell adhesion molecule (NCAM) (Nelson and Finger, 1993).…”