title: SPCA2 regulates Orai1 trafficking and store independent Ca2+ entry in a model of lactation.
abstract: An unconventional interaction between SPCA2, an isoform of the Golgi secretory pathway Ca(2+)-ATPase, and the Ca(2+) influx channel Orai1, has previously been shown to contribute to elevated Ca(2+) influx in breast cancer derived cells. In order to investigate the physiological role of this interaction, we examined expression and localization of SPCA2 and Orai1 in mouse lactating mammary glands. We observed co-induction and co-immunoprecipitation of both proteins, and isoform-specific differences in the localization of SPCA1 and SPCA2. Three-dimensional cultures of normal mouse mammary epithelial cells were established using lactogenic hormones and basement membrane. The mammospheres displayed elevated Ca(2+) influx by store independent mechanisms, consistent with upregulation of both SPCA2 and Orai1. Knockdown of either SPCA2 or Orai1 severely depleted Ca(2+) influx and interfered with mammosphere differentiation. We show that SPCA2 is required for plasma membrane trafficking of Orai1 in mouse mammary epithelial cells and that this function can be replaced, at least in part, by a membrane-anchored C-terminal domain of SPCA2. These findings clearly show that SPCA2 and Orai1 function together to regulate Store-independent Ca(2+) entry (SICE), which mediates the massive basolateral Ca(2+) influx into mammary epithelia to support the large calcium transport requirements for milk secretion.
authors.affiliation: Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Brandie M
authors.initials: BM
authors.lastname: Cross
authors.forename: Anniesha
authors.initials: A
authors.lastname: Hack
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Reinhardt
authors.forename: Rajini
authors.initials: R
authors.lastname: Rao
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling; D000252:Calcium-Transporting ATPases / Q000737:chemistry / Q000502:physiology*; D005260:Female; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006801:Humans; D007774:Lactation / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism; D051379:Mice; D057507:Mice, 129 Strain; D000071740:ORAI1 Protein; D020033:Protein Isoforms / Q000502:physiology; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D018874:Spheroids, Cellular / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D000071740:ORAI1 Protein; C520430:Orai1 protein, mouse; D020033:Protein Isoforms; C528285:SPCA2 protein, mouse; D000252:Calcium-Transporting ATPases; D002118:Calcium