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ZnT2 regulates lysosomal acidification and biogenesis during mammary gland involution
Author(s) -
Rivera Olivia C.,
Hennigar Stephen R.,
Lee Sooyeon,
Kelleher Shan L.
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.448.4
Subject(s) - involution (esoterism) , medicine , endocrinology , biogenesis , biology , microbiology and biotechnology , v atpase , chemistry , atpase , biochemistry , enzyme , consciousness , neuroscience , gene
Precocious involution may be an underlying cause of early infant weaning or overt lactation failure. The initial phase of mammary gland (MG) involution is characterized by lysosomal‐mediated cell death (LCD), which requires extensive upregulation of lysosomal biogenesis, acidification and activity. We recently showed that in response to the pro‐involution signal TNFα, the zinc transporter ZnT2 traffics from secretory vesicles to lysosomes, is critical for lysosome biogenesis, and is associated with LCD and activation of MG involution. Moreover, obesity‐induced inflammation is also associated with ZnT2 and zinc accumulation in lysosomes, and the promotion of LCD and precocious involution. However, the role of ZnT2 in LCD is currently not understood. We hypothesized that ZnT2 modulates proton transport, mediating lysosomal biogenesis, acidification, and activity, thereby driving proper execution of MG involution. Histology of involuting MGs from ZnT2‐null mice (ZnT2ko) had reduced alveolar regression, more closely resembling a lactating MG than that of involuting MGs from their wild‐type (wt) littermates. The MG area repopulated by adipocytes only increased by 12% in ZnT2ko mice compared to a 37% increase in wt mice ( P <0.001). Furthermore, activation of the involution marker Stat3 was significantly reduced in ZnT2ko involuting MGs ( P <0.05), indicating insufficient involution. Co‐immunoprecipitation studies of ZnT2 and the vacuolar ATPase (v‐ATPase) proton transporter in cultured mammary epithelial cells (MECs) revealed that ZnT2 interacts with both the cytoplasmic (V1) and membrane‐embedded (V0) subunits of v‐ATPase, suggesting a role for ZnT2 in v‐ATPase assembly and proton transport. Consistent with this finding, ZnT2 over‐expression in MECs significantly increased the number, size and acidification of lysosomes, while ZnT2‐attenuated MECs were not able to undergo lysosome biogenesis or acidification. Immunofluorescent imaging revealed that lysosomal abundance of V1 was reduced by ~75% ( P <0.01) which was associated with a significant decrease in lysosome abundance ( P <0.001) and size ( P <0.01) in the involuting MGs of ZnT2ko mice compared to wt mice, suggesting impaired lysosomal biogenesis. Our results establish ZnT2 as a critical regulator of v‐ATPase activity and lysosomal acidification, which is essential for the activation of involution. Given the identification of numerous mutations and non‐synonymous genetic variants in ZnT2 that result in impaired ZnT2 function and breast dysfunction, these findings suggest that genetic variants in ZnT2 may modulate lysosome biogenesis and activity, thereby affecting lactation duration. Support or Funding Information Intramural Funds from Penn State Hershey College of Medicine, Department of Surgery