Failure of autophagy maturation in CD38 deficient coronary arterial myocytes due to inhibition of dynein‐mediated autophagosome trafficking (865.3)

Abstract

Autophagic flux refers to the process that lysosome traffics and fuses with autophagosomes (APs) leading to their maturation to form autophagolysosomes (APLs) and consequent breakdown of autophagic contents by lysosomal proteases. However, the mechanisms controlling autophagic flux, particularly autophagy maturation in vascular cells are poorly understood. Here, we revealed a role of CD38, an enzyme that metabolizes NADP+ into NAADP, in autophagy maturation in coronary arterial myocytes (CAMs). In vivo, CD38‐/‐ fed the Western diet showed increased accumulation of APs in coronary arterial media compared to CD38+/+ mice, suggesting that CD38 gene deletion results in a deranged autophagic process. In primary cultured CAMs, a novel flow cytometric CytoID analysis showed that 7‐ketocholesterol (7‐Ket, an atherogenic stimulus and autophagy inducer)‐induced APs formation was similar between CD38+/+ and CD38‐/‐ CAMs when their autophagic flux was blocked by choloquine, which indicates that CD38 is not involved in APs formation. Tandem RFP‐GFP‐LC3B assay demonstrated that CD38 gene deletion markedly enhanced 7‐Ket‐induced accumulation of APs but decreased the formation of APLs in CAMs, indicating a role of CD38 in autophagy flux. Furthermore, loss of CD38 function was implicated in impaired autophagy maturation rather than in lysosomal alkalization or protease inhibition‐associated blockade of autophagic flux because CD38‐/‐ and CD38+/+ CAMs had similar lysosomal pH and lysosomal protease activities. Importantly, CD38 gene deletion markedly inhibited 7‐Ket‐induced dynein activation and APs trafficking, which were associated with attenuated lysosomal Ca2+ release. Taken together, these results suggest that CD38 plays a critical role in the control of dynein‐mediated APs trafficking and fusion with lysosomes thus determining autophagy maturation in CAMs under atherogenic stimulation.Grant Funding Source: Supported by NIH grants HL057244, HL091464 and HL075316