Figure 2.

Lysosome ion channels and transporters. The lysosomal lumen contains a battery of soluble hydrolytic enzymes that degrade proteins (proteases), triglycerides (lysosomal acid lipase; LAL), glycoproteins (glycosidases), heparan sulphate (sulfatases), and nucleic acids (nucleases, RNAase and DNAse). Lysosomal ion channels and transporters include vATPase; vacuolar H⁺-ATPase (proton pump), chloride channel (ClC); ClC family that exchanges cytosolic Cl⁻ for lysosomal H⁺ (ClC-6 and ClC-7), K⁺ channels (BK). Non-selective cation channels include Transient Receptor Potential Cation Channel (TRPML); permeable to Ca²⁺, Na⁺, K⁺, Zn²⁺ and Fe²⁺, P2X4 channel; permeable to Ca²⁺, Na⁺ and K⁺ and two-pore channels (TPC); permeable to H⁺, Ca²⁺ and Na⁺. Ion transporters include Na⁺/H⁺ exchangers (NHEs) and Ca²⁺/H⁺ exchangers (CHX).