Lysosomal targeting of autophagosomes by the TECPR domain of TECPR2

TECPR2 (tectonin beta-propeller repeat containing 2) is a large, multi-domain protein comprised of an amino-terminal WD domain, a middle unstructured region and a carboxy-terminal TEPCR domain comprises of six TECPR repeats followed by a functional LIR motif. Human <i>TECPR2</i> mutations are linked to spastic paraplegia type 49 (SPG49), a hereditary neurodegenerative disorder. Here we show that basal macroautophagic/autophagic flux is impaired in SPG49 patient fibroblasts in the form of accumulated autophagosomes. Ectopic expression of either full length TECPR2 or the TECPR domain rescued autophagy in patient fibroblasts in a LIR-dependent manner. Moreover, this domain is recruited to the cytosolic leaflet of autophagosomal and lysosomal membranes in a LIR- and VAMP8-dependent manner, respectively. These findings provide evidence for a new role of the TECPR domain in particular, and TECPR2 in general, in lysosomal targeting of autophagosomes <i>via</i> association with Atg8-family proteins on autophagosomes and VAMP8 on lysosomes. <b>Abbreviations:</b> HOPS: homotypic fusion and vacuole protein sorting; LIR: LC3-interacting region; SPG49: spastic paraplegia type 49; STX17: syntaxin 17; TECPR2: tectonin beta-propeller repeat containing 2; VAMP8: vesicle associated membrane protein 8

TECPR2（tectonin beta-propeller repeat containing 2，即含凝血球蛋白β螺旋重复序列2）是一种大型多结构域蛋白，由氨基端WD结构域、中间无序区域以及羧基端TECPR结构域组成；该TECPR结构域包含6个TECPR重复序列，后续连接一个功能性LIR（LC3-interacting region，LC3相互作用基序）基序。人类*TECPR2*基因突变与49型痉挛性截瘫（spastic paraplegia type 49, SPG49）相关，后者是一种遗传性神经退行性疾病。本研究证实，SPG49患者成纤维细胞中的基础巨自噬/自噬流受损，表现为自噬体异常堆积。对全长TECPR2或TECPR结构域进行异位表达，均可通过LIR依赖的方式挽救患者成纤维细胞中的自噬缺陷。此外，该结构域分别以LIR依赖与VAMP8（vesicle associated membrane protein 8，囊泡相关膜蛋白8）依赖的方式，被招募至自噬体膜与溶酶体膜的胞质侧单层。上述研究结果证实，TECPR结构域尤为如此，以及TECPR2整体而言，在自噬体通过结合自噬体上的Atg8家族蛋白与溶酶体上的VAMP8，进而实现向溶酶体的靶向递送的过程中，发挥了全新的作用。**缩写：** HOPS：同型融合与液泡蛋白分选复合体（homotypic fusion and vacuole protein sorting）；LIR：LC3相互作用基序（LC3-interacting region）；SPG49：49型痉挛性截瘫（spastic paraplegia type 49）；STX17：突触融合蛋白17（syntaxin 17）；TECPR2：含凝血球蛋白β螺旋重复序列2（tectonin beta-propeller repeat containing 2）；VAMP8：囊泡相关膜蛋白8（vesicle associated membrane protein 8）