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Ankyrin-B is required for intracellular sorting of structurally diverse Ca2+ homeostasis proteins.

Tuvia S, Buhusi M, Davis L, Reedy M, Bennett V - J. Cell Biol. (1999)

Bottom Line: Ankyrin-B is associated with intracellular vesicles, but is not colocalized with the bulk of SERCA 1 or ryanodine receptor type 1 in skeletal muscle.These data provide the first evidence of a physiological requirement for ankyrin-B in intracellular targeting of the calcium homeostasis machinery of striated muscle and immune system, and moreover, support a catalytic role that does not involve permanent stoichiometric complexes between ankyrin-B and targeted proteins.Similar mechanisms involving ankyrins may be essential for segregation of functionally defined proteins within specialized regions of the plasma membrane and within the Ca(2+) homeostasis compartment of the ER.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute and Departments of Cell Biology and Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA.

ABSTRACT
This report describes a congenital myopathy and major loss of thymic lymphocytes in ankyrin-B (-/-) mice as well as dramatic alterations in intracellular localization of key components of the Ca(2+) homeostasis machinery in ankyrin-B (-/-) striated muscle and thymus. The sarcoplasmic reticulum (SR) and SR/T-tubule junctions are apparently preserved in a normal distribution in ankyrin-B (-/-) skeletal muscle based on electron microscopy and the presence of a normal pattern of triadin and dihydropyridine receptor. Therefore, the abnormal localization of SR/ER Ca ATPase (SERCA) and ryanodine receptors represents a defect in intracellular sorting of these proteins in skeletal muscle. Extrapolation of these observations suggests defective targeting as the basis for abnormal localization of ryanodine receptors, IP3 receptors and SERCA in heart, and of IP3 receptors in the thymus of ankyrin-B (-/-) mice. Mis-sorting of SERCA 2 and ryanodine receptor 2 in ankyrin-B (-/-) cardiomyocytes is rescued by expression of 220-kD ankyrin-B, demonstrating that lack of the 220-kD ankyrin-B polypeptide is the primary defect in these cells. Ankyrin-B is associated with intracellular vesicles, but is not colocalized with the bulk of SERCA 1 or ryanodine receptor type 1 in skeletal muscle. These data provide the first evidence of a physiological requirement for ankyrin-B in intracellular targeting of the calcium homeostasis machinery of striated muscle and immune system, and moreover, support a catalytic role that does not involve permanent stoichiometric complexes between ankyrin-B and targeted proteins. Ankyrin-B is a member of a family of adapter proteins implicated in restriction of diverse proteins to specialized plasma membrane domains. Similar mechanisms involving ankyrins may be essential for segregation of functionally defined proteins within specialized regions of the plasma membrane and within the Ca(2+) homeostasis compartment of the ER.

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Musculoskeletal defects, neonatal myopathy, and loss of expression of 220- and 150-kD ankyrin-B polypeptides in striated muscle and thymus of ankyrin-B (−/−) mice. (A) Photograph of a 3-d-old ankyrin-B (−/−) mouse and a (+/+) littermate (left); higher magnification of the same mice (right). Note pronounced kyphosis (arrowhead) and winged scapula (arrow) of the (−/−) animal. (B) Serum creatine kinase activity of neonatal ankyrin-B (+/+), (+/−), and (−/−) mice. (C) Electron micrographs of skeletal muscle (quadriceps) from ankyrin-B (+/+) (left) and ankyrin-B (−/−) (right) mice (7-d-old littermates) at the same magnification. Note occasional focal disarray of Z-bands and sarcomeres (yellow asterisk) in ankyrin-B (−/−) muscle. (D) Immunoblots of brain, thymus, heart, and skeletal muscle of ankyrin-B (+/+) and (−/−) mice with rabbit affinity-purified antibody against ankyrin-B COOH terminus. Lanes with brain polypeptides were exposed one-fourth the time of lanes with other tissues.
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Figure 1: Musculoskeletal defects, neonatal myopathy, and loss of expression of 220- and 150-kD ankyrin-B polypeptides in striated muscle and thymus of ankyrin-B (−/−) mice. (A) Photograph of a 3-d-old ankyrin-B (−/−) mouse and a (+/+) littermate (left); higher magnification of the same mice (right). Note pronounced kyphosis (arrowhead) and winged scapula (arrow) of the (−/−) animal. (B) Serum creatine kinase activity of neonatal ankyrin-B (+/+), (+/−), and (−/−) mice. (C) Electron micrographs of skeletal muscle (quadriceps) from ankyrin-B (+/+) (left) and ankyrin-B (−/−) (right) mice (7-d-old littermates) at the same magnification. Note occasional focal disarray of Z-bands and sarcomeres (yellow asterisk) in ankyrin-B (−/−) muscle. (D) Immunoblots of brain, thymus, heart, and skeletal muscle of ankyrin-B (+/+) and (−/−) mice with rabbit affinity-purified antibody against ankyrin-B COOH terminus. Lanes with brain polypeptides were exposed one-fourth the time of lanes with other tissues.

Mentions: Ankyrin-B (−/−) mice display abnormal posture with kyphosis and winged scapulae (Fig. 1 A). Creatine kinase activity also is elevated about fourfold in sera from ankyrin-B (−/−) mice compared with normal littermates, based on determinations of seven litters at ages ranging from postnatal day 1 to 13 (Fig. 1 B). Measurements of neonatal heterozygotes revealed some mice (8 out of 26) with a two- to threefold increase and other mice with normal levels of serum creatine kinase activity. For comparison, patients with congenital myopathies or mild muscular dystrophy frequently have normal levels or small elevation in levels of creatine kinase activity.


Ankyrin-B is required for intracellular sorting of structurally diverse Ca2+ homeostasis proteins.

Tuvia S, Buhusi M, Davis L, Reedy M, Bennett V - J. Cell Biol. (1999)

Musculoskeletal defects, neonatal myopathy, and loss of expression of 220- and 150-kD ankyrin-B polypeptides in striated muscle and thymus of ankyrin-B (−/−) mice. (A) Photograph of a 3-d-old ankyrin-B (−/−) mouse and a (+/+) littermate (left); higher magnification of the same mice (right). Note pronounced kyphosis (arrowhead) and winged scapula (arrow) of the (−/−) animal. (B) Serum creatine kinase activity of neonatal ankyrin-B (+/+), (+/−), and (−/−) mice. (C) Electron micrographs of skeletal muscle (quadriceps) from ankyrin-B (+/+) (left) and ankyrin-B (−/−) (right) mice (7-d-old littermates) at the same magnification. Note occasional focal disarray of Z-bands and sarcomeres (yellow asterisk) in ankyrin-B (−/−) muscle. (D) Immunoblots of brain, thymus, heart, and skeletal muscle of ankyrin-B (+/+) and (−/−) mice with rabbit affinity-purified antibody against ankyrin-B COOH terminus. Lanes with brain polypeptides were exposed one-fourth the time of lanes with other tissues.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2169334&req=5

Figure 1: Musculoskeletal defects, neonatal myopathy, and loss of expression of 220- and 150-kD ankyrin-B polypeptides in striated muscle and thymus of ankyrin-B (−/−) mice. (A) Photograph of a 3-d-old ankyrin-B (−/−) mouse and a (+/+) littermate (left); higher magnification of the same mice (right). Note pronounced kyphosis (arrowhead) and winged scapula (arrow) of the (−/−) animal. (B) Serum creatine kinase activity of neonatal ankyrin-B (+/+), (+/−), and (−/−) mice. (C) Electron micrographs of skeletal muscle (quadriceps) from ankyrin-B (+/+) (left) and ankyrin-B (−/−) (right) mice (7-d-old littermates) at the same magnification. Note occasional focal disarray of Z-bands and sarcomeres (yellow asterisk) in ankyrin-B (−/−) muscle. (D) Immunoblots of brain, thymus, heart, and skeletal muscle of ankyrin-B (+/+) and (−/−) mice with rabbit affinity-purified antibody against ankyrin-B COOH terminus. Lanes with brain polypeptides were exposed one-fourth the time of lanes with other tissues.
Mentions: Ankyrin-B (−/−) mice display abnormal posture with kyphosis and winged scapulae (Fig. 1 A). Creatine kinase activity also is elevated about fourfold in sera from ankyrin-B (−/−) mice compared with normal littermates, based on determinations of seven litters at ages ranging from postnatal day 1 to 13 (Fig. 1 B). Measurements of neonatal heterozygotes revealed some mice (8 out of 26) with a two- to threefold increase and other mice with normal levels of serum creatine kinase activity. For comparison, patients with congenital myopathies or mild muscular dystrophy frequently have normal levels or small elevation in levels of creatine kinase activity.

Bottom Line: Ankyrin-B is associated with intracellular vesicles, but is not colocalized with the bulk of SERCA 1 or ryanodine receptor type 1 in skeletal muscle.These data provide the first evidence of a physiological requirement for ankyrin-B in intracellular targeting of the calcium homeostasis machinery of striated muscle and immune system, and moreover, support a catalytic role that does not involve permanent stoichiometric complexes between ankyrin-B and targeted proteins.Similar mechanisms involving ankyrins may be essential for segregation of functionally defined proteins within specialized regions of the plasma membrane and within the Ca(2+) homeostasis compartment of the ER.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute and Departments of Cell Biology and Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA.

ABSTRACT
This report describes a congenital myopathy and major loss of thymic lymphocytes in ankyrin-B (-/-) mice as well as dramatic alterations in intracellular localization of key components of the Ca(2+) homeostasis machinery in ankyrin-B (-/-) striated muscle and thymus. The sarcoplasmic reticulum (SR) and SR/T-tubule junctions are apparently preserved in a normal distribution in ankyrin-B (-/-) skeletal muscle based on electron microscopy and the presence of a normal pattern of triadin and dihydropyridine receptor. Therefore, the abnormal localization of SR/ER Ca ATPase (SERCA) and ryanodine receptors represents a defect in intracellular sorting of these proteins in skeletal muscle. Extrapolation of these observations suggests defective targeting as the basis for abnormal localization of ryanodine receptors, IP3 receptors and SERCA in heart, and of IP3 receptors in the thymus of ankyrin-B (-/-) mice. Mis-sorting of SERCA 2 and ryanodine receptor 2 in ankyrin-B (-/-) cardiomyocytes is rescued by expression of 220-kD ankyrin-B, demonstrating that lack of the 220-kD ankyrin-B polypeptide is the primary defect in these cells. Ankyrin-B is associated with intracellular vesicles, but is not colocalized with the bulk of SERCA 1 or ryanodine receptor type 1 in skeletal muscle. These data provide the first evidence of a physiological requirement for ankyrin-B in intracellular targeting of the calcium homeostasis machinery of striated muscle and immune system, and moreover, support a catalytic role that does not involve permanent stoichiometric complexes between ankyrin-B and targeted proteins. Ankyrin-B is a member of a family of adapter proteins implicated in restriction of diverse proteins to specialized plasma membrane domains. Similar mechanisms involving ankyrins may be essential for segregation of functionally defined proteins within specialized regions of the plasma membrane and within the Ca(2+) homeostasis compartment of the ER.

Show MeSH
Related in: MedlinePlus