SPEG Controls Calcium Reuptake Into the Sarcoplasmic Reticulum Through Regulating SERCA2a by Its Second Kinase-Domain.

Abstract

RATIONALE:

SPEG (Striated muscle preferentially expressed protein kinase) has 2 kinase-domains and is critical for cardiac development and function. However, it is not clear how these 2 kinase-domains function to maintain cardiac performance.

OBJECTIVE:

To determine the molecular functions of the 2 kinase-domains of SPEG.

METHODS AND RESULTS:

A proteomics approach identified SERCA2a (sarcoplasmic/endoplasmic reticulum calcium ATPase 2a) as a protein interacting with the second kinase-domain but not the first kinase-domain of SPEG. Furthermore, the second kinase-domain of SPEG could phosphorylate Thr484 on SERCA2a, promote its oligomerization and increase calcium reuptake into the sarcoplasmic/endoplasmic reticulum in culture cells and primary neonatal rat cardiomyocytes. Phosphorylation of SERCA2a by SPEG enhanced its calcium-transporting activity without affecting its ATPase activity. Depletion of Speg in neonatal rat cardiomyocytes inhibited SERCA2a-Thr484 phosphorylation and sarcoplasmic reticulum calcium reuptake. Moreover, overexpression of SERCA2aThr484Ala mutant protein also slowed sarcoplasmic reticulum calcium reuptake in neonatal rat cardiomyocytes. In contrast, domain mapping and phosphorylation analysis revealed that the first kinase-domain of SPEG interacted and phosphorylated its recently identified substrate JPH2 (junctophilin-2). An inducible heart-specific Speg knockout mouse model was generated to further study this SPEG-SERCA2a signal nexus in vivo. Inducible deletion of Speg decreased SERCA2a-Thr484 phosphorylation and its oligomerization in the heart. Importantly, inducible deletion of Speg inhibited SERCA2a calcium-transporting activity and impaired calcium reuptake into the sarcoplasmic reticulum in cardiomyocytes, which preceded morphological and functional alterations of the heart and eventually led to heart failure in adult mice.

CONCLUSIONS:

Our data demonstrate that the 2 kinase-domains of SPEG may play distinct roles to regulate cardiac function. The second kinase-domain of SPEG is a critical regulator for SERCA2a. Our findings suggest that SPEG may serve as a new target to modulate SERCA2a activation for treatment of heart diseases with impaired calcium homeostasis.

• Authors: Chao Quan, Min Li, Qian Du, Qiaoli Chen, Hong Wang, David Campbell, Lei Fang, Bin Xue, Carol MacKintosh, Xiang Gao, Kunfu Ouyang, Hong Yu Wang, Shuai Chen
• Journal: Circulation research (Circ Res) Vol. 124 Issue 5 Pg. 712-726 (03 2019) ISSN: 1524-4571 [Electronic] United States
• PMID: 30566039 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Atp2a2 protein, rat
• Muscle Proteins
• Protein Serine-Threonine Kinases
• Speg protein, mouse
• Speg protein, rat
• Myosin-Light-Chain Kinase
• Sarcoplasmic Reticulum Calcium-Transporting ATPases
• Atp2a2 protein, mouse

Topics

• Animals
• Calcium Signaling
• Cardiomyopathy, Dilated (enzymology, genetics, pathology, physiopathology)
• Disease Models, Animal
• HEK293 Cells
• Heart Failure (enzymology, genetics, pathology, physiopathology)
• Humans
• Mice, Inbred C57BL
• Mice, Knockout
• Muscle Proteins (genetics, metabolism)
• Myocytes, Cardiac (enzymology, pathology)
• Myosin-Light-Chain Kinase (genetics, metabolism)
• Phosphorylation
• Protein Binding
• Protein Interaction Domains and Motifs
• Protein Serine-Threonine Kinases
• Rats
• Sarcoplasmic Reticulum (enzymology, pathology)
• Sarcoplasmic Reticulum Calcium-Transporting ATPases (genetics, metabolism)