Zn+2 transporter 5 (ZnT-5, ZnT-like transporter 1, hZTL1, solute carrier family 30 member 5, SLC30A5, ZNT5, ZNTL1, ZTL1, UNQ863/PRO1879)
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Function
- Zn+2 transporter
- may be a transporter of Zn+2 into beta cells in order to form insulin crystals
- partly regulates cellular Zn+2 homeostasis
- required with ZNT7 for the activation of Zn+2-requiring enzymes, alkaline phosphatases (ALPs)
- transports Zn+2 into the lumens of the Golgi & vesicular compartments where ALPs locate, thus, converting apo-ALPs to holo-ALPs
- required with ZNT6 & ZNT7 for the activation of TNAP
- hetero-oligomer
- interacts with ZNT6
Structure
- belongs to the cation diffusion facilitator (CDF) transporter (TC 2.A.4) family; SLC30A subfamily
- histidine-rich loop is essential for ZNT5 & ZNT6 hetero-oligomeric complexes to activate TNA
Compartment
- Golgi, trans-Golgi network membrane
- perimeter of granules
- localizes to the brush border membrane of the enterocyte
- concentrated in early compartments of the secretory pathway such as COPII-coated vesicles
Alternative splicing
named isoforms=2
Expression
- ubiquitously expressed
- highly expressed in pancreas, liver & kidney
- expressed abundantly in insulin- containing beta cells
- undetectable in other endocrine cell types including glucagon-secreting alpha cells & most acinar cells
- increased intracellular Zn+2 level, resulting from extracellular Zn+2 supplementation, do NOT induce any up- or down-regulation of gene expression
- up-regulated by Zn+2 depletion