The secretory pathway Ca2+/Mn2+-ATPase 2 is a Golgi-localized pump with high affinity for Ca2+ ions.
Accumulation of Ca(2+) into the Golgi apparatus is mediated by sarco(endo)plasmic reticulum Ca(2+)-ATPases (SERCAs) and by secretory pathway Ca(2+)-ATPases (SPCAs). Mammals and birds express in addition to the housekeeping SPCA1 (human gene name ATP2C1, cytogenetic position 3q22.1) a homologous SPCA2 isoform (human gene name ATP2C2, cytogenetic position 16q24.1). We show here that both genes present an identical exon/intron layout. We confirmed that hSPCA2 has the ability to transport Ca(2+), demonstrated its Mn(2+)-transporting activity, showed its Ca(2+)- and Mn(2+)-dependent phosphoprotein intermediate formation, and documented the insensitivity of these functional activities to thapsigargin inhibition. The mRNA encoding hSPCA2 showed a limited tissue expression pattern mainly confined to the gastrointestinal and respiratory tract, prostate, thyroid, salivary, and mammary glands. Immunocytochemical localization in human colon sections presented a typical apical juxtanuclear Golgi-like staining. The expression in COS-1 cells allowed the direct demonstration of (45)Ca(2+) (K(0.5) = 0.27 microm) or (54)Mn(2+) transport into an A23187-releasable compartment.
Vanoevelen
Jo
J
Laboratorium voor Fysiologie, Katholieke Universiteit Leuven, Campus Gasthuisberg O/N, Belgium.
Dode
Leonard
L
Van Baelen
Kurt
K
Fairclough
Rebecca J
RJ
Missiaen
Ludwig
L
Raeymaekers
Luc
L
Wuytack
Frank
F
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D019556:COS Cells; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism / Q000502:physiology*; D003106:Colon / Q000378:metabolism; D005091:Exons; D006056:Golgi Apparatus / Q000378:metabolism*; D006801:Humans; D019811:Hydroxylamine / Q000737:chemistry; D007150:Immunohistochemistry; D007438:Introns; D007477:Ions; D007700:Kinetics; D008345:Manganese / Q000378:metabolism; D008969:Molecular Sequence Data; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D014018:Tissue Distribution; D014162:Transfection
D007477:Ions; D020033:Protein Isoforms; D012333:RNA, Messenger; D019811:Hydroxylamine; D000001:Calcimycin; D008345:Manganese; D019284:Thapsigargin; D000251:Adenosine Triphosphatases; C452183:ATP2C2 protein, human; D000252:Calcium-Transporting ATPases; D002118:Calcium