Ligand-receptor interaction, cellular

Cellular processes involving the classic ligand-receptor interaction and beyond (e.g., G-proteins, second messenger systems)... 

The quantitation of steric effects is complex at best and challenging in all other situations, particularly at the molecular level. An added level of confusion comes into play when attempts are made to delineate size and shape. Nevertheless, sterics are of overwhelming importance in ligand-receptor interactions as well as in transport phenomena in cellular systems. The first steric parameter to be quantified and used in QSAR studies was Taft s constant (157). is defined as... 

Drug-receptor interactions may quantitatively differ among rapidly converting multiple receptor states that are induced by agonist binding. While most studies commonly focus on analysis of ligand-receptor interactions and cellular responses under presumed steady-state conditions, experimental techniques available for the quantitative analysis of drug-receptor interactions with transient receptor conformational... 

One of the possible applications directly related to multivalent ligand-receptor interactions will be the design of polymeric inhibitors which specifically bind receptors existing on cellular membranes to inhibit the uptake of biological substrates via the receptors. For example, there are many kinds of intestinal membrane transporters for... 

B. Ligand-receptor interaction- E. Cellular and tissular functional ... 

Fig. 3.1 Schematic representation of the series of biochemical steps leading from ligand-receptor interaction to the cellular and physiological responses. LI, L2 and D stand for ligand and drug, respectively. R1 and R2 represent specific membrane receptors that recognize Li and L2. El — n are effector proteins, generally enzymes, modulated by receptor activation or by drugs acting as inhibitors. S is a specific substrate.

The regulation of cell function by extrinsic factors occurs through a series of second-messenger signals that are initiated by ligand-receptor interaction and are responsible from the modulation of both the intensity and the nature of cellular responses. In this manner, second messengers exert control over principal cellular events, such as metabolism, secretion, strucmre, and replication. ... 

Figure 1 Bias in the chemokine system and other 7TMRs. Biased signaling describes the ability of a receptor to induce different signaling pathways or cellular events. Thereby, different ligands may activate different pathways via the same receptor (ligand bias, A), or the same ligand induces different outcomes at different receptors (receptor bias, B). Also the cell or tissue that "hosts" the ligand receptor interaction can modulate the induced signaling pathway (tissue bias, C).

Some biological processes involve the adhesion of a particular molecule to a specific locus of a membrane or tissue (ligand-receptor interaction) referring to cellular interactions (cytoadhesion) or to mucosal adhesion mucoadhesion), but this topic will not be covered in this chapter see for example (Thomas and Peppas 2006). 

---