title: Integrity of the network sarcoplasmic reticulum in skeletal muscle requires small ankyrin 1.
abstract: Small ankyrin 1 (sAnk1; Ank1.5) is a ~20 kDa protein of striated muscle that concentrates in the network compartment of the sarcoplasmic reticulum (nSR). We used siRNA targeted to sAnk1 to assess its role in organizing the sarcoplasmic reticulum (SR) of skeletal myofibers in vitro. siRNA reduced sAnk1 mRNA and protein levels and disrupted the organization of the remaining sAnk1. Sarcomeric proteins were unchanged, but two other proteins of the nSR, SERCA and sarcolipin, decreased significantly in amount and segregated into distinct structures containing sarcolipin and sAnk1, and SERCA, respectively. Exogenous sAnk1 restored SERCA to its normal distribution. Ryanodine receptors and calsequestrin in the junctional SR, and L-type Ca(2+) channels in the transverse tubules were not reduced, although their striated organization was mildly altered. Consistent with the loss of SERCA, uptake and release of Ca(2+) were significantly inhibited. Our results show that sAnk1 stabilizes the nSR and that its absence causes the nSR to fragment into distinct membrane compartments.
authors: Department of Biochemistry and Molecular Biology, Therapeutics University of Maryland, Baltimore, MD 21201,  USA.
authors: Maegen A
authors: MA
authors: Ackermann
authors: Andrew P
authors: AP
authors: Ziman
authors: John
authors: J
authors: Strong
authors: Yinghua
authors: Y
authors: Zhang
authors: April K
authors: AK
authors: Hartford
authors: Christopher W
authors: CW
authors: Ward
authors: William R
authors: WR
authors: Randall
authors: Aikaterini
authors: A
authors: Kontrogianni-Konstantopoulos
authors: Robert J
authors: RJ
authors: Bloch
mesh_terms: D000818:Animals; D017487:Ankyrins / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D011510:Proteolipids / Q000235:genetics / Q000378:metabolism; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism
chemical_list: C540195:Ank1 protein, rat; D017487:Ankyrins; C506945:Atp2a1 protein, rat; D009124:Muscle Proteins; D011510:Proteolipids; C077258:sarcolipin; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases