Yasuhiro Hakamata

Primary structure and distribution of a novel ryanodine receptor/calcium release channel from rabbit brain

The complete amino acid sequence of a novel ryanodine receptor/calcium release channel from rabbit brain has been deduced by cloning and sequence analysis of the EDNA. This protein is composed of 4872 amino acids and shares characteristic structural features with the skeletal muscle and cardiac ryanodine receptors. RNA blot hybridization analysis shows that the brain ryanodine receptor is abundantly expressed in corpus striatum, thalamus and hippocampus, whereas the cardiac ryanodine receptor is more uniformly expressed in the brain. The brain ryanodine receptor gene is transcribed also in smooth muscle.

Primary structure and functional expression from cDN A of the cardiac ryanodine receptor/calcium release channel

The sequence of 4968 (or 4976 with an insertion) amino acids composing the ryanodine receptor from rabbit cardiac sarcoplasmic reticulum has been deduced by cloning and sequencing the cDNA. This protein is homologous in amino acid sequence and shares characteristic structural features with the skeletal muscle ryanodine receptor. Xenopus oocytes injected with mRNA derived from the cardiac ryanodine receptor cDNA exhibit Ca2+‐dependent Cl− current in response to caffeine, which indicates the formation of functional calcium release channels. RNA blot hybridization analysis with a probe specific for the cardiac ryanodine receptor mRNA shows that the stomach and brain contain a hybridizable RNA species with a size similar to that of the cardiac mRNA. This result, in conjunction with cloning and analysis of partial cDNA sequences, suggests that the brain contains a cardiac type of ryanodine receptor mRNA.

Involvement of the brain type of ryanodine receptor in T-cell proliferation

Cloning and sequence analysis of cDNA showed that the brain type of ryanodine receptor (RYR) is expressed in human Jurkat T‐lymphocyte cells. Fura‐2 measurements revealed that the RYR in T‐cells functions as a ryanodine‐sensitive, caffeine‐insensitive Ca2+ release channel. Furthermore, ryanodine stimulated proliferation and altered the growth pattern of cultured human T‐cells when added together with FK506.

Molecular cloning and characterization of a human brain ryanodine receptor.

We have cloned and sequenced the cDNA of the human brain ryanodine receptor (RyR3), which is composed of 4866 amino acids and shares characteristic structural features with the rabbit RyR3. Northern blot analysis shows that the human RyR3 mRNA is abundantly expressed in hippocampus, caudate nucleus and amygdala as well as in skeletal muscle. The human RyR3 mRNA is also detected in several cell lines derived from human brain tumors. Functional expression of RyR3 and a chimeric RyR suggests that RyR3 forms a calcium‐release channel with a very low Ca2+ sensitivity.

Characterization of brain-type ryanodine receptor permanently expressed in Chinese hamster ovary cells

To clarify a function of brain-type ryanodine receptor (RyR3) and its regulation, we established a stable cell line expressing rabbit RyR3 by transfection of Chinese hamster ovary cells (CHO cells) with the cDNA and investigated characteristics of the RyR3. Scatchard analysis of [3H]-ryanodine binding to the membrane from CHO cells expressing RyR3 showed two distinct binding sites. The Kd values of high and low affinity binding sites were 1.92 and 25.9 nM, respectively. [3H]-ryanodine binding to the membrane from CHO cells expressing RyR3 was dependent on pCa. Extracellular Ca2+ (2-10 mM) and high concentration (more than 30 mM) of caffeine activated the RyR3 in CHO cells and increased its intracellular Ca2+ concentration. The enhancement of [3H]-ryanodine binding to the membrane from CHO cells expressing RyR3 was observed by bromoeudistomin D (BED), a caffeine-like powerful Ca2+ releaser, at pCa 5.5. Stably expressed RyR3 in CHO is useful for characterization of its function.

Response of the extramedullary lung plasmacytoma with pleural effusion to chemotherapy

Abstract An elderly patient with an extramedullary lung plasmacytoma and subsequent pleural effusion is described. The presence of abnormal plasma cells in the pleural fluid led to diagnosis. Histologically similar conditions such as multiple myeloma and solitary myeloma of bone were ruled out by clinical evaluation. These neoplasms usually occur in the head and neck area and are not characterized by paraprotein accumulation. Few cases in the lung have been reported. We describe a case of extramedullary plasmacytoma of the lung with plasmacytoma-induced pleural effusion and the presence of monoclonal paraprotein in both the serum and urine. Chemotherapy with melphalan was effective in reducing the size of the plasmacytoma, and pleurodesis was used to manage the pleural effusion.