Overlapping functions between Lamp2a and Lamp2b in cardiac autophagy.

LAMP2 is a ubiquitously expressed protein critical for autophagy. Alternative splicing gives rise to three isoforms. However, the roles of major LAMP2 isoforms in the heart are not known. To address this knowledge gap, we generated lamp2a and lamp2b knockout (KO) mice to investigate the role of these isoforms in heart function and autophagy. Deletion of either Lamp2a or Lamp2b did not alter cardiac structure or function. Lack of all LAMP2 isoforms led to increased cardiac fibrosis and reduced survival during pressure overload, which were not observed in lamp2a or lamp2b KO mice. Also, LAMP2B loss did not affect levels of the autophagy markers LC3-II and SQSTM1/p62. Conversely, LAMP2A was upregulated in hearts lacking LAMP2B, potentially preserving autophagy and cardiac function. Reintroducing LAMP2A in lamp2 KO mice effectively reduced autophagosome accumulation and improved cardiac function. Overall, these data support LAMP2 isoform functional redundancy in the myocardium under pathological conditions.Abbreviations: AAV: adeno-associated virus; ACTA2: actin alpha 2, smooth muscle, aorta; CMA: chaperone-mediated autophagy; KO: knockout; LAMP2: lysosomal-associated membrane protein 2; LV: Left ventricle; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; NPPA: natriuretic peptide type A; NPPB: natriuretic peptide type B; SQSTM1/p62: sequestosome 1; PBS: phosphate-buffered saline; PCR: polymerase chain reaction; TAC: transverse aortic constriction; WT: wild type.