Ryanodine receptors isoforms

Ogawa Y, Kurebayashi N, Murayama T (1999) Ryanodine receptor isoforms in excitation-contraction coupling. Adv Biophys 36 27-64... 

Paul We have been talking about the SR as a site of release, as if it were one thing. There is superficial SR, deep SR and ER, with three different ryanodine receptor isoforms and at least two different SERCAs. Are these on the same vesicles, or different vesicles What s the role of the ER Do they communicate with one another There are a lot of questions about this compartmentalization and vectorial release. The mitochondria also intrigue me the SR can still function quite well after CCCP (carbonyl cyanide ///-chlorophenylhydrazone), which inhibits mitochondrial Ca2+ uptake. 

Blaustein We have seen the same thing in cultured cells we see no evidence for CICR. There are two possible explanations. First, the smooth muscle cells have a different ryanodine receptor isoform. Second, the rate of rise of Ca2+ is much slower in smooth muscle. In cardiac muscle there is a blast of Ca2+, with a rapid rise. Perhaps the slower effect means that smooth muscle cells don t get to threshold at the ryanodine receptor. The question is whether it is the channel or the process in general. 

Yang, T., Ta, T. A., Pessah, I. N., and Allen, P. D. (2003). Functional Defects in Six Ryanodine Receptor Isoform-1 (RyRl) Mutations Associated with Malignant Hyperthermia and their Impact on Skeletal Excitation-Contraction Coupling. J Biol Chem 278(28) 25722-30. 

Ryanodine Receptor. Table 1 Three Mammalian RyR isoforms... 

The Ca release channel is also known as the ryanodine receptor (RYR). There are two isoforms of this... 

Human myometrium has been demonstrated to contain the mRNA of all three isoforms of the ryanodine receptor, although type 1 and 3 mRNA are the most abundant (Martin et al 1999). Similarly, mRNA encoding the three types of InsP3 receptor are present in human myometrium (Morgan et al 1996). In cultured human myocytes, a lacy network can be outlined by using antibodies against... 

Dettling M, Sander T, Weber M, Steinlein OK. Mutation analysis of the ryanodine receptor gene isoform 3 (RYR3) in recurrent neuroleptic malignant syndrome. J Clin Psychopharmacol 2004 24 471-3. 

Mammals possess three isoforms of the ryanodine receptor RyRl and RyR2, distributed primarily in skeletal and cardiac muscle, respectively, and RyR3 distributed more heterogeneously. Insects, however, express a single form of the receptor, sharing only 47% sequence homology [9]. Comparative studies were conducted to determine Rynaxypyr s ability to activate mammalian RyRs. 

Ryanodine receptors (RyR) mediate the release of calcium from intracellular stores of the sarcoplasmic/endoplasmic reticulum (SR/ER) following a small calcium influx via voltage-gated calcium channels of the cytoplasmic membrane after depolarization. The process, referred to as calcium-induced calcium release, triggers muscle contraction after electrical excitation in mammalian cardiac as well as in insect striated muscles (I). Three RyR isoforms exist in mammals Type 1, which is predominantly expressed in skeletal muscles Type 2, which is expressed in cardiac muscle and the more ubiquitously expressed Type 3 2 . 

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