Manganese-induced turnover of TMEM165

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Congenital disorders of glycosylation (CDG) are inherited diseases affecting protein glycosylation.
• TMEM165 deficiency causes a CDG subtype linked to disrupted Golgi manganese homeostasis.
• Manganese (Mn2+) supplementation can rescue glycosylation defects in TMEM165-deficient cells.

Purpose of the Study:

• To investigate TMEM165's role as a manganese-sensitive Golgi protein.
• To analyze the impact of manganese exposure on TMEM165 stability and function.
• To characterize the functional consequences of TMEM165 mutations found in CDG patients.

Main Methods:

• Cellular exposure to varying manganese concentrations.
• Analysis of TMEM165 protein levels and localization via degradation assays.
• Functional assessment of glycosylation in cells expressing wild-type and mutant TMEM165.
• Mutation analysis of TMEM165 variants (R126H and E108G).

Main Results:

• TMEM165 is identified as a novel Golgi protein sensitive to manganese.
• High manganese concentrations induce lysosomal degradation of TMEM165.
• The TMEM165-CDG variant E108G is insensitive to manganese-induced degradation.
• The E108G mutation does not impair TMEM165's function in Golgi glycosylation.

Conclusions:

• TMEM165 is a manganese-sensitive Golgi protein crucial for cellular manganese homeostasis.
• The glutamic acid at position 108 (E108) within the cytosolic ELGDK motif is critical for manganese-induced TMEM165 degradation.
• The E108G mutation confers resistance to manganese-induced degradation without abolishing TMEM165's glycosylation function, offering insights into TMEM165-CDG pathogenesis.