Annexins A1 and A2 are recruited to larger lysosomal injuries independently of ESCRTs to promote repair

Abstract

Damaged lysosomes can be repaired by calcium release-dependent recruitment of the ESCRT machinery. However, the involvement of annexins, another group of calcium-responding membrane repair proteins, has not been fully addressed. Here, we show that although all ubiquitously expressed annexins (ANXA1, A2, A4, A5, A6, A7, and A11) localize to damaged lysosomes, only ANXA1 and ANXA2 are important for repair. Their recruitment is calcium-dependent, ESCRT-independent, and selective towards lysosomes with large injuries. Lysosomal leakage was more severe when ANXA1 or ANXA2 was depleted compared to that of ESCRT components. These findings suggest that ANXA1 and ANXA2 constitute an additional repair mechanism that serves to minimize leakage from damaged lysosomes.

Collapse of late endosomal pH elicits a rapid Rab7 response via V-ATPase and RILP.

“…Since the majority of LEs did not show membrane damage after LLOMe, we next investigated the alternative hypothesis that leaking luminal content from damaged LYS might cause phenotypic changes in size and number of Rab7 LEs in response to LMP. In particular, local Ca 2+ release from LYS after LLOMe is required for both ESCRT-dependent and - independent repair mechanisms (Skowyra et al, 2018; Yim et al, 2022; Niekamp et al, 2022; Tan and Finkel, 2022; Radulovic et al, 2022). Cytosolic Ca 2+ release can also elicit signaling through adaptor proteins (Clapham, 2007) that have profound impacts on membrane trafficking (Chadwick et al, 2021), and thus might be the communicable signal for phenotypic changes to Rab7+ LE size and number.…”

“…First, milder LMP (small membrane disruption) initiates mechanisms that directly repair the damaged lysosomal membrane within minutes. Together, endosomal sorting complex required for transport (ESCRT) (Skowyra et al, 2018; Radulovic et al, 2018; Jia et al, 2020a; Bohannon and Hanson, 2020), annexins A1/A2 (Yim et al, 2022), sphingomyelin scramblases (Niekamp et al, 2022), and phosphatidyl-inositol-4-phosphate (PI4P) production (Tan and Finkel, 2022; Radulovic et al, 2022) facilitate direct membrane repair. These repair mechanisms have all been shown to be dependent on local Ca 2+ release from damaged lysosomes.…”

Monitoring and assessment of lysosomal membrane damage in cultured cells using the high-content imager

“…LLOMe treatments with different conditions, such as concentration or treatment time, may induce different degrees or sizes of lysosomal membrane injury. 6 , 7 , 8 Based on these membrane injuries, distinct molecules may be recruited to repair or remove damaged lysosomes.…”

The ESCRT Machinery: Remodeling, Repairing, and Sealing Membranes

“…An additional factor could be the Parkinson s-disease-related leucine-rich repeat kinase 2 (LRRK2), which upon lysosome damage triggers the recruitment of the small GTPase Rab8A and subsequently the ESCRT-III protein CHMP4B to damaged organelles in macrophages [129]. Interestingly, Ca 2+ efflux can also trigger additional ESCRT-independent lysosomal repair mechanisms mediated by annexins A1 and A2 [130] and sphingomyelin scrambling and turnover [131].…”