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The Ca2+/H+ antiporter TMEM165 expression, localization in the developing, lactating and involuting mammary gland parallels the secretory pathway Ca2+ ATPase (SPCA1)

Timothy A. Reinhardt, John D. Lippolis, Randy E. Sacco
Biochemical and Biophysical Research Communications 2014 v.445 no.2 pp. 417-421
Golgi apparatus, adenosinetriphosphatase, antiporters, calcium, cells, exhibitions, knockout mutants, lactation, mammary glands, milk, plasma membrane, pregnancy
Plasma membrane Ca(2+)-ATPase 2 (PMCA2) knockout mice showed that ~ 60 % of calcium in milk is transported across the mammary cells apical membrane by PMCA2. The remaining milk calcium is thought to arrive via the secretory pathway through the actions of secretory pathway Ca(2+)-ATPase’s 1 and/or 2 (SPCA1 and 2). However, another secretory pathway calcium transporter was recently described. The question becomes whether this Golgi Ca(2+)/H+ antiporter (TMEM165) is expressed sufficiently in the Golgi of lactating mammary tissue to be a relevant contributor to secretory pathway mammary calcium transport. TMEM165 shows marked expression on day one of lactation when compared to timepoints prepartum. At peak lactation TMEM165 expression was 25 times greater than that of early pregnancy. Forced cessation of lactation resulted in a rapid ~50 % decline in TMEM165 expression at 24 hours of involution and TMEM165 expression declined 95% at 96 hours involution. It is clear that the timing, magnitude of TMEM165 expression and its Golgi location supports a role for this Golgi Ca(2+) /H+ antiporter as a contributor to mammary Golgi calcium transport needs, in addition to the better-characterized roles of SPCA1&2.