Receptor dihydropyridine

DICR (depolarization-induced Ca2+ release) is Ca2+ release triggered by depolarization of the sarcolemma. In skeletal muscle, conformational change in the voltage sensor (a 1S subunit of the dihydropyridine receptor) in the T-tubule is directly transmitted to the... 

Dihydropyridine receptor (DHPR) is a member of voltage-dqiendent Ca2+ channels (CaVi, L-type), which specifically binds to dihydropyridine derivatives, a group of the Ca2+ channel blockers. Cav 1.1 works as the voltage sensor for skeletal muscle contraction, and Cay 1.2, as Ca2+-influx channel for cardiac muscle contraction. 

Figure 49-8. Diagram of the relationships among the sarcolemma (plasma membrane), a T tubule, and two cisternae of the sarcoplasmic reticulum of skeletal muscle (not to scale). The T tubule extends inward from the sarcolemma. A wave of depolarization, initiated by a nerve impulse, is transmitted from the sarcolemma down the T tubule. It is then conveyed to the Ca release channel (ryanodine receptor), perhaps by interaction between it and the dihydropyridine receptor (slow Ca voltage channel), which are shown in close proximity. Release of Ca from the Ca release channel into the cytosol initiates contraction. Subsequently, Ca is pumped back into the cisternae of the sarcoplasmic reticulum by the Ca ATPase (Ca pump) and stored there, in part bound to calsequestrin.

Figure 49-9. Possible chain of events leading to opening of the Ca release channel. As indicated in the text, the Ca voltage channel and the Ca release channel have been shown to interact with each other in vitro via specific regions in their polypeptide chains. (DHPR, dihydropyridine receptor RYR1, ryanodine receptor 1.)...

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Tanabe T, Beam KG, Adams BA, Niidome T, Numa S 1990 Regions of the skeletal muscle dihydropyridine receptor critical for excitation-contraction coupling. Nature 346 567-569... 

To characterize the preparation, determine marker enzymes, e.g., p-nitrophenyl phosphatase (PNPase), ouabain-sensitive Na,K-dependent ATPase, or dihydropyridine receptor complex (L-type voltage dependent calcium channel). 

A special coupling between extracellular Ca influx and the ryanodin receptor exists in muscle cells. There, a voltage-dependent Ca channel, the dihydropyridine receptor, is coupled directly to the cytoplasmic domain of the ryanodin receptor (see Fig. 6.7a). A depolarization of the cell membrane is transmitted in this system via an electromechanical coupling directly to the gating state of the ryanodin receptor. 

Skeletal muscle is activated by nerve impulses which induce Ca2+ release through the action of a voltage sensor, a protein also known as the dihydropyridine receptor,wx together with a calcium release channel known as the ryanodine... 

The release channels open in response to an incompletely characterized linkage to the voltage sensor that is present in the T-tubule membrane and is known as the dihydropyridine receptor 240/245 This too, is a Ca2+ channel, which opens in response to arrival of an action potential (nerve impulse see Chapter 30) that move along the T-tubule membrane. Because the... 

Kugler G, Weiss RG, Flucher BE, Grabner M (2004) Structural requirements of the dihydropyridine receptor alphal S II-III loop for skeletal-type excitation-contraction coupling. J Biol Chem 279 4721-4728. 

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