TNF-α/ENO1 signaling facilitates testicular phagocytosis by directly activating Elmo1 gene expression in mouse Sertoli cells

Phagocytic clearance of apoptotic germ cells (GCs), as well as residual bodies released from developing spermatids, is critical for Sertoli cells (SCs) to maintain inner environment homeostasis within the testis. However, the molecular mechanisms controlling the phagocytosis are ill defined. Here, we identify a new role for alpha-enolase (ENO1), a key enzyme during glycolysis, as a molecule that facilitates testicular phagocytosis via transactivation of the engulfment and cell motility 1 (Elmo1) gene. Using immunohistochemistry and double-labeling immunofluorescence, ENO1 was observed to be expressed exclusively in the nuclei of SCs and its expression correlated with the completion of SC differentiation. By incubating TM4 cells with different pharmacological inhibitors and establishing TM4^Tnfr1-/- cells, we demonstrated that SC-specific expression of ENO1 was under a delicate paracrine control from apoptotic GCs. In turn, persistent blockade of ENO1 expression by a validated small interfering RNA protocol resulted in the disturbance of spermatogenesis and impairment of male fertility. Furthermore, using ChIP, electrophoretic mobility shift and luciferase reporter assays, we showed that, in the presence of apoptotic GCs, ENO1 binds to the distal region of the Elmo1 promoter and facilitates transactivation of the Elmo1 gene. In agreement, overexpression of ELMO1 ameliorated ENO1 deficiency-induced impairment of phagocytosis in TM4 cells. These data reveal a novel role for SC-specific expression of ENO1 in regulating phagocytosis in testis, identify tumor necrosis factor-α and ELMO1 as critical upstream and downstream factors in mediating ENO1 action, and have important implications for our understanding of paracrine control of SC function by adjacent GCs.