Cell receptor complexes modeling

More complex models must carefully consider additional factors such as the receptor structure of helper T cells and allow for, what in reality, is a less than perfect lock and key match between antibody and antigen. For the latter case, Stauffer [staufF92] describes two schemes in which more than one type of antibody fits a given antigen and more than one type of antigen corresponds to a given antibody. 

Recently, a putative olfactory receptor from Drosophila, Or43a (Clyne et al., 1999 Vosshall et al., 1999), has been expressed in Xenopus laevis oocytes (Wetzel et al., 2001). The receptor expressed in a heterologous cell system was activated by four odorants, i.e. cyclohexanone, cyclohexanol, benzaldehyde, and benzyl alcohol (Wetzel et al., 2001). These experiments not only provided direct evidence for the function of the Or gene, but also demonstrated that the olfactory receptor can be stimulated without an odorant-binding protein. It was demonstrated earlier that PBP was not necessary to obtain pheromone-dependent responses in cultured olfactory receptor neurons of Manduca sexta (Stengl et al., 1992). The possibility that OBPs have been produced in vitro and were present in cultured ORNs could not be excluded. The same argument can not be raised for the heterologous expression of the Drosophila olfactory receptor. While the evidence that Xenopus oocytes responded to odorants in the absence of OBPs does not support the OBP-odorant complex model, it also demonstrated that OBPs are essential for the kinetics of the olfactory system (see below). 

If Arabidopsis PEN1 is a component of the endosomal complex responsible for endocytosis of the LPS/LOS-receptor complex, similar to endocytosis of the LPS-complex in mammals and the observed endocytosis of LPS in tobacco cells discussed above, an increased induction of innate immune responses would, presumably, have been observed in LOS-stimulated Arabidopsis penl mutants compared to the wild-type. Although we favour a model in which PEN1 is involved in exocytosis required for Xcc LOS triggered immunity in Arabidopsis, we cannot discount an alternate role in endocytosis. Importantly the findings indicate that... 

Fig. 1. A model for the control of the luteinizing hormone receptor. LH interacts with a specific receptor (RLh) in Leydig cells which results in the activation of several transducing systems. This is followed by an uncoupling (desensitization) from one or more of the transducing systems. The latter may transiently remain active. The LH receptor complex is internalized and then dissociated in endocytic vesicles. LH is degraded in the lysosomes. The LH receptor synthesis can be controlled by several hormones including oestradiol, prolactin and growth hormone.

---