Schild, Detlev, and Diego Restrepo. Transduction Mechanisms in Vertebrate Olfactory Receptor Cells. Physiol. Rev. 78: 429–466, 1998. — Considerable progress has been made in the understanding of tr...

Transduction Mechanisms in Vertebrate Olfactory Receptor Cells

Odorant-binding proteins (OBPs) are low-molecular-weight soluble proteins highly concentrated in the nasal mucus of vertebrates and in the sensillar lymph of insects. Their affinity toward odors and pheromones suggests a role in olfactory perception, but their physiological function has not been clearly defined. Several members of this class of proteins have been isolated and characterized both in insects and vertebrates; in most species two or three types of OBPs are expressed in the nasal area. Vertebrates OBPs show significant sequence similarity with a superfamily of soluble carrier proteins called lipocalins. They include some proteins of particular interest that are thought to be involved in the mechanism of releasing and modulating chemical messages with pheromonal activity. The data on vertebrate OBPs are here reviewed together with the most relevant information on related proteins. Theories and models of the physiological functions of odorant-binding proteins are presented and discussed.

Odorant-binding proteins

Although motor deficits are gaining attention in autism research much less attention has been paid to the physical activity patterns in this group of children. The participants in this study were a group of children with autism spectrum disorder (N = 72) between the ages of 9-18 years. This cross-sectional study explored the physical activity patterns of seventy-two children with autism spectrum disorder as they aged. Results indicated significant differences between the mean time spent in moderate to vigorous physical activity and the mean time spent in sedentary activity. Older children with autism spectrum disorder are significantly more physically inactive, compared to younger children. Physical activity programs and interventions need to address this deficit, in physical activity. Children with autism have a similar trend in physical activity patterns compared to their peers without autism; associated benefits and future research will be discussed.

/pdf/the-physical-activity-patterns-of-children-with-autism-3gm6jyfvrr.pdf

The physical activity patterns of children with autism

The molecular basis of odor recognition

Since many cells respond to ligand occupation of appropriate receptors by undergoing increased phosphoinositide turnover,' we have investigated the possibility that olfactory neurons respond to odorants by this pathway. Olfactory receptors and their associated transduction elements are localized in the dendritic cilia of olfactory neurons?-' A method was therefore developed for the isolation of olfactory cilia from the channel catfish (Ictalurus punctatus) with improved yield. The cilia were detached by calcium shock treatment of the olfactory epithelium in the presence of 300 mM sucrose. Following centrifugation to remove the deciliated epithelium, the cilia were centrifuged at 28,000 x g, resuspended, and layered on a 45% (wt/wt) sucrose cushion. The gradient was centrifuged at 50,000 X g and the cilia were collected from the top of the sucrose cushion, whereas pigmented material was pelleted at the bottom of the cushion. Under these conditions, the yield of cilia was 165 * 9 pg protein/g tissue (n = 5 preparations). Using the same conditions, but with no sucrose in the deciliation medium, the yield of cilia was 92 ? 30 pg protein/g tissue (n = 3). The isolated preparations were characterized by transmission electron microscopy, SDS-polyacrylamide gel electrophoresis, and Western blotting to identify individual protein components such as t~bu l in .~ The isolated cilia exhibited phosphatidylinositol-4,5-bisphosphate phosphodiesterase (PIP,-PDE, E.C.3.1.4.11) activity, which was enriched about fourfold over the activity of the deciliated epithelium! This enzyme catalyzes the rapid hydrolysis of PIP , to form the potential second messengers diacylglycerol and inositol-1,4,5-trisphosphate.' Electrophysiological studies have demonstrated previously that amino acids are olfactory stimuli for the catfish.'. The isolated cilia preparations contained receptors for odorant amino acids as demonstrated by tritiated L-amino acid binding measurements? PIP,PDE activity was stimulated in the isolated preparations in the presence of odorant amino acids. For example, the enzyme activity was stimulated 57% over basal level in the presence of 5 pA4 L-alanine (TABLE 1). Furthermore, the PIP,-PDE activity was also stimulated 39% over control levels in the presence of 0.1 pA4 GTP (TABLE 2). The nonhydrolyzable GTP analogues, Gpp( NH)p and GTPyS, were equally effective in their ability to stimulate PIP,-PDE activity, but

Odorant‐ and Guanine Nucleotide‐Stimulated Phosphoinositide Turnover in Olfactory Ciliaa

The recently introduced frog olfactory cilia preparation (Chen and Lancet, 1984; Pace et al., 1985) has been useful for studies of molecular chemosensory mechanisms. Here we describe in detail the properties of this cilia preparation. The "calcium shock" procedure leads to a complete removal of the cilia from the olfactory epithelial surface. Isolated cilia constitute segments of proximal regions with 9 X 2 + 2 microtubular arrangement and a large proportion of membrane vesicles, probably derived from the ciliary distal segments. Polypeptides unique to the olfactory cilia preparation, compared to a control preparation of palate respiratory cilia, are identified by Coomassie brilliant blue staining, silver staining, and radiolabeled lectin overlays, as well as by biosynthetic labeling with 35S-methionine in epithelial explants and protein phosphorylation in isolated cilia. The olfactory cilia preparation contains odorant-sensitive adenylate cyclase, which is absent in control membranes from deciliated epithelium. High activities of tyrosine and serine/threonine protein kinases are also present. The olfactory cilia preparation described should be instrumental in the further elucidation of the biochemistry and molecular biology of vertebrate olfaction.

https://www.jneurosci.org/content/jneuro/6/8/2146.full.pdf

Isolated frog olfactory cilia: a preparation of dendritic membranes from chemosensory neurons

Polypeptide gp95: a unique glycoprotein of olfactory cilia with transmembrane receptor properties

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Isolated frog olfactory cilia: a preparation of dendritic membranes from chemosensory neurons

Polypeptide gp95: a unique glycoprotein of olfactory cilia with transmembrane receptor properties