Figure 3.

Autophagy induced by Vitamin D. After being taken up by the cell, Vitamin D is catalyzed into 1,25-D3 by 25-hydroxylase and D-1-hydroxylase. 1,25-D3 binds to VDR to activate autophagy through down-regulating mTOR and Bcl-2, and increasing NO, Ca²⁺ and cathelicidin. Both JNK1 and DAPK (death-associated kinase) can mediate autophagy by regulating the activity of PI3KC3. NO impairs the activity of JNK1, and Ca²⁺ enhances the activity of DAPK. Bcl-2 can bind to Beclin 1 to inhibit the activity of PI3KC3. Cathelicidin mediates autophagy through increasing Beclin 1. Mtb can induce autophagy by the up-regulation of D-1-hydroxylase, VDR and cathelicidin, and the down-regulation of Bcl-2. Cathlicidin can be induced by Mtb DNA-mediated stimulation of TLR9