Limits...
Calpain 3 deficiency affects SERCA expression and function in the skeletal muscle.

Toral-Ojeda I, Aldanondo G, Lasa-Elgarresta J, Lasa-Fernández H, Fernández-Torrón R, López de Munain A, Vallejo-Illarramendi A - Expert Rev Mol Med (2016)

Bottom Line: In CAPN3-deficient myotubes, we found decreased levels of SERCA 1 and 2 proteins, while mRNA levels remained comparable with control myotubes.Also, we found a significant reduction in SERCA function that resulted in impairment of Ca2+ homeostasis, and elevated basal intracellular [Ca2+] in human myotubes.Altogether, our results indicate that CAPN3 deficiency leads to degradation of SERCA proteins and Ca2+ dysregulation in the skeletal muscle.

View Article: PubMed Central - PubMed

Affiliation: Neuroscience Area,Biodonostia Research Institute,San Sebastian,Spain.

ABSTRACT
Limb-girdle muscular dystrophy type 2A (LGMD2A) is a form of muscular dystrophy caused by mutations in calpain 3 (CAPN3). Several studies have implicated Ca2+ dysregulation as an underlying event in several muscular dystrophies, including LGMD2A. In this study we used mouse and human myotube cultures, and muscle biopsies in order to determine whether dysfunction of sarco/endoplasmatic Ca2+-ATPase (SERCA) is involved in the pathology of this disease. In CAPN3-deficient myotubes, we found decreased levels of SERCA 1 and 2 proteins, while mRNA levels remained comparable with control myotubes. Also, we found a significant reduction in SERCA function that resulted in impairment of Ca2+ homeostasis, and elevated basal intracellular [Ca2+] in human myotubes. Furthermore, small Ankyrin 1 (sAnk1), a SERCA1-binding protein that is involved in sarcoplasmic reticulum integrity, was also diminished in CAPN3-deficient fibres. Interestingly, SERCA2 protein was patently reduced in muscles from LGMD2A patients, while it was normally expressed in other forms of muscular dystrophy. Thus, analysis of SERCA2 expression may prove useful for diagnostic purposes as a potential indicator of CAPN3 deficiency in muscle biopsies. Altogether, our results indicate that CAPN3 deficiency leads to degradation of SERCA proteins and Ca2+ dysregulation in the skeletal muscle. While further studies are needed in order to elucidate the specific contribution of SERCA towards muscle degeneration in LGMD2A, this study constitutes a reasonable foundation for the development of therapeutic approaches targeting SERCA1, SERCA2 or sAnk1.

No MeSH data available.


Related in: MedlinePlus

A working model of CAPN3 functions at the sarcoplasmic reticulum network in theskeletal muscle. Under physiological conditions, CAPN3 stabilises SERCA1 and SERCA2protein complexes at the sarcoplasmic reticulum network. However, CAPN3 deficiencyinduces SERCA protein ubiquitination and degradation, and results in a loss of calciumhomeostasis. Binding of sAnk1 to SERCA1 may help stabilise SERCA1 protein complexesunder pathological conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4836212&req=5

fig07: A working model of CAPN3 functions at the sarcoplasmic reticulum network in theskeletal muscle. Under physiological conditions, CAPN3 stabilises SERCA1 and SERCA2protein complexes at the sarcoplasmic reticulum network. However, CAPN3 deficiencyinduces SERCA protein ubiquitination and degradation, and results in a loss of calciumhomeostasis. Binding of sAnk1 to SERCA1 may help stabilise SERCA1 protein complexesunder pathological conditions.

Mentions: In search for pathways affected by CAPN3 deficiency that may be related with a decrease inSERCA proteins, we found that levels of sAnk1 are reduced in CAPN3-deficient muscles andmyotubes. Also, abnormal nuclear localisation of sAnk1 was observed in CAPN3-deficientmuscles. sAnk1 is an integral protein of the SR network that, like CAPN3, concentratesaround Z-discs and M-lines (Ref. 41). This proteinhas been shown to interact with the giant sarcomeric proteins titin and obscurin, thus,connecting the SR with the contractile apparatus (Refs 42, 43). Since sAnk1 is essential for SERCAexpression and localisation as well as for the integrity of the SR network compartment,reduction of sAnk1 levels observed in CAPN3-deficient fibres might be indicative of adisrupted SR architecture and SR-related proteins such as SERCA (Refs 19, 20).Co-immunoprecipitation analysis in human muscles revealed interaction between CAPN3 and theSR proteins SERCA1, SERCA2 and sAnk1. We propose that under physiological conditions, CAPN3stabilises SERCA1 and SERCA2 protein complexes at the SR network. In LGMD2A, CAPN3deficiency induces ubiquitination and degradation of SERCA proteins and ultimately resultsin a loss of calcium homeostasis. Binding of sAnk1 to SERCA1 may help stabilise SERCA1protein complexes under pathological conditions, when CAPN3 levels are moderately reduced(Fig. 7). Figure 7.


Calpain 3 deficiency affects SERCA expression and function in the skeletal muscle.

Toral-Ojeda I, Aldanondo G, Lasa-Elgarresta J, Lasa-Fernández H, Fernández-Torrón R, López de Munain A, Vallejo-Illarramendi A - Expert Rev Mol Med (2016)

A working model of CAPN3 functions at the sarcoplasmic reticulum network in theskeletal muscle. Under physiological conditions, CAPN3 stabilises SERCA1 and SERCA2protein complexes at the sarcoplasmic reticulum network. However, CAPN3 deficiencyinduces SERCA protein ubiquitination and degradation, and results in a loss of calciumhomeostasis. Binding of sAnk1 to SERCA1 may help stabilise SERCA1 protein complexesunder pathological conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4836212&req=5

fig07: A working model of CAPN3 functions at the sarcoplasmic reticulum network in theskeletal muscle. Under physiological conditions, CAPN3 stabilises SERCA1 and SERCA2protein complexes at the sarcoplasmic reticulum network. However, CAPN3 deficiencyinduces SERCA protein ubiquitination and degradation, and results in a loss of calciumhomeostasis. Binding of sAnk1 to SERCA1 may help stabilise SERCA1 protein complexesunder pathological conditions.
Mentions: In search for pathways affected by CAPN3 deficiency that may be related with a decrease inSERCA proteins, we found that levels of sAnk1 are reduced in CAPN3-deficient muscles andmyotubes. Also, abnormal nuclear localisation of sAnk1 was observed in CAPN3-deficientmuscles. sAnk1 is an integral protein of the SR network that, like CAPN3, concentratesaround Z-discs and M-lines (Ref. 41). This proteinhas been shown to interact with the giant sarcomeric proteins titin and obscurin, thus,connecting the SR with the contractile apparatus (Refs 42, 43). Since sAnk1 is essential for SERCAexpression and localisation as well as for the integrity of the SR network compartment,reduction of sAnk1 levels observed in CAPN3-deficient fibres might be indicative of adisrupted SR architecture and SR-related proteins such as SERCA (Refs 19, 20).Co-immunoprecipitation analysis in human muscles revealed interaction between CAPN3 and theSR proteins SERCA1, SERCA2 and sAnk1. We propose that under physiological conditions, CAPN3stabilises SERCA1 and SERCA2 protein complexes at the SR network. In LGMD2A, CAPN3deficiency induces ubiquitination and degradation of SERCA proteins and ultimately resultsin a loss of calcium homeostasis. Binding of sAnk1 to SERCA1 may help stabilise SERCA1protein complexes under pathological conditions, when CAPN3 levels are moderately reduced(Fig. 7). Figure 7.

Bottom Line: In CAPN3-deficient myotubes, we found decreased levels of SERCA 1 and 2 proteins, while mRNA levels remained comparable with control myotubes.Also, we found a significant reduction in SERCA function that resulted in impairment of Ca2+ homeostasis, and elevated basal intracellular [Ca2+] in human myotubes.Altogether, our results indicate that CAPN3 deficiency leads to degradation of SERCA proteins and Ca2+ dysregulation in the skeletal muscle.

View Article: PubMed Central - PubMed

Affiliation: Neuroscience Area,Biodonostia Research Institute,San Sebastian,Spain.

ABSTRACT
Limb-girdle muscular dystrophy type 2A (LGMD2A) is a form of muscular dystrophy caused by mutations in calpain 3 (CAPN3). Several studies have implicated Ca2+ dysregulation as an underlying event in several muscular dystrophies, including LGMD2A. In this study we used mouse and human myotube cultures, and muscle biopsies in order to determine whether dysfunction of sarco/endoplasmatic Ca2+-ATPase (SERCA) is involved in the pathology of this disease. In CAPN3-deficient myotubes, we found decreased levels of SERCA 1 and 2 proteins, while mRNA levels remained comparable with control myotubes. Also, we found a significant reduction in SERCA function that resulted in impairment of Ca2+ homeostasis, and elevated basal intracellular [Ca2+] in human myotubes. Furthermore, small Ankyrin 1 (sAnk1), a SERCA1-binding protein that is involved in sarcoplasmic reticulum integrity, was also diminished in CAPN3-deficient fibres. Interestingly, SERCA2 protein was patently reduced in muscles from LGMD2A patients, while it was normally expressed in other forms of muscular dystrophy. Thus, analysis of SERCA2 expression may prove useful for diagnostic purposes as a potential indicator of CAPN3 deficiency in muscle biopsies. Altogether, our results indicate that CAPN3 deficiency leads to degradation of SERCA proteins and Ca2+ dysregulation in the skeletal muscle. While further studies are needed in order to elucidate the specific contribution of SERCA towards muscle degeneration in LGMD2A, this study constitutes a reasonable foundation for the development of therapeutic approaches targeting SERCA1, SERCA2 or sAnk1.

No MeSH data available.


Related in: MedlinePlus