title: Distinct regions of triadin are required for targeting and retention at the junctional domain of the sarcoplasmic reticulum.
abstract: Ca2+ release, which is necessary for muscle contraction, occurs at the j-SR (junctional domain of the sarcoplasmic reticulum). It requires the assembly of a large multiprotein complex containing the RyR (ryanodine receptor) and additional proteins, including triadin and calsequestrin. The signals which drive these proteins to the j-SR and how they assemble to form this multiprotein complex are poorly understood. To address aspects of these questions we studied the localization, dynamic properties and molecular interactions of triadin. We identified three regions, named TR1 (targeting region 1), TR2 and TR3, that contribute to the localization of triadin at the j-SR. FRAP experiments showed that triadin is stably associated with the j-SR and that this association is mediated by TR3. Protein pull-down experiments indicated that TR3 contains binding sites for calsequestrin-1 and that triadin clustering can be enhanced by binding to calsequestrin-1. These findings were confirmed by FRET experiments. Interestingly, the stable association of triadin to the j-SR was significantly decreased in myotubes from calsequestrin-1 knockout mice. Taken together, these results identify three regions in triadin that mediate targeting to the j-SR and reveal a role for calsequestrin-1 in promoting the stable association of triadin to the multiprotein complex associated with RyR.
authors: Daniela
authors: D
authors: Rossi
authors: *Department of Molecular and Developmental Medicine, University of Siena, Via A Moro 2, 53100 Siena, Italy.
authors: Cristina
authors: C
authors: Bencini
authors: *Department of Molecular and Developmental Medicine, University of Siena, Via A Moro 2, 53100 Siena, Italy.
authors: Marina
authors: M
authors: Maritati
authors: *Department of Molecular and Developmental Medicine, University of Siena, Via A Moro 2, 53100 Siena, Italy.
authors: Francesca
authors: F
authors: Benini
authors: *Department of Molecular and Developmental Medicine, University of Siena, Via A Moro 2, 53100 Siena, Italy.
authors: Stefania
authors: S
authors: Lorenzini
authors: *Department of Molecular and Developmental Medicine, University of Siena, Via A Moro 2, 53100 Siena, Italy.
authors: Enrico
authors: E
authors: Pierantozzi
authors: *Department of Molecular and Developmental Medicine, University of Siena, Via A Moro 2, 53100 Siena, Italy.
authors: Angela Maria
authors: AM
authors: Scarcella
authors: Cecilia
authors: C
authors: Paolini
authors: Feliciano
authors: F
authors: Protasi
authors: Vincenzo
authors: V
authors: Sorrentino
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D002451:Cell Compartmentation / Q000502:physiology; D002478:Cells, Cultured; D016503:Drug Delivery Systems; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008861:Microsomes / Q000737:chemistry / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D041681:NIH 3T3 Cells; D025941:Protein Interaction Mapping / Q000379:methods; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry; D012519:Sarcoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; C070048:triadin