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Calpain-2 specifically cleaves Junctophilin-2 at the same site as Calpain-1 but with less efficacy
Journal article   Open access   Peer reviewed

Calpain-2 specifically cleaves Junctophilin-2 at the same site as Calpain-1 but with less efficacy

Jinxi Wang, Grace Ciampa, Dong Zheng, Qian Shi, Biyi Chen, E Dale Abel, Tianqing Peng, Duane D Hall and Long-Sheng Song
Biochemical journal, Vol.478(19), pp.3539-3553
10/15/2021
DOI: 10.1042/BCJ20210629
PMCID: PMC8589432
PMID: 34524407
url
https://doi.org/10.1042/BCJ20210629View
Published (Version of record) Open Access

Abstract

Calpain proteolysis contributes to the pathogenesis of heart failure but the calpain isoforms responsible and their substrate specificities have not been rigorously defined. One substrate, Junctophilin-2 (JP2), is essential for maintaining junctional cardiac dyads and excitation-contraction coupling. We previously demonstrated that mouse JP2 is cleaved by calpain-1 (CAPN1) between Arginine 565 (R565) and Threonine 566 (T566). Recently, calpain-2 (CAPN2) was reported to cleave JP2 at a novel site between Glycine 482 (G482) and Threonine 483 (T483). We aimed to directly compare the contributions of each calpain isoform, their Ca2+ sensitivity, and their cleavage site selection for JP2. We find CAPN1, CAPN2 and their requisite CAPNS1 regulatory subunit are induced by pressure overload stress that is concurrent with JP2 cleavage. Using in vitro calpain cleavage assays, we demonstrate that CAPN1 and CAPN2 cleave JP2 into similar 75 kD N-terminal (JP2NT) and 25 kD C-terminal fragments (JP2CT) with CAPNS1 co-expression enhancing proteolysis. Deletion mutagenesis shows both CAPN1 and CAPN2 require R565/T566 but not G482/T483. When heterologously expressed, the JP2CT peptide corresponding to R565/T566 cleavage approximates the 25 kD species found during cardiac stress while the C-terminal peptide from potential cleavage at G482/T483 produces a 35 kD product. Similar results were obtained for human JP2. Finally, we show that CAPN1 has higher Ca2+ sensitivity and cleavage efficacy than CAPN2 on JP2 and other cardiac substrates including cTnT, cTnI and β2-spectrin. We conclude that CAPN2 cleaves JP2 at the same functionally conserved R565/T566 site as CAPN1 but with less efficacy and suggest heart failure may be targeted through specific inhibition of CAPN1.
 Transfection Animals Arginine - metabolism Calpain - genetics Calpain - metabolism Disease Models, Animal Glycine - metabolism Heart Failure - metabolism HEK293 Cells Humans Male Membrane Proteins - genetics Membrane Proteins - metabolism Mice Muscle Proteins - genetics Muscle Proteins - metabolism Mutagenesis, Site-Directed - methods Myocytes, Cardiac - metabolism Proteolysis Signal Transduction - genetics Threonine - metabolism

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