A novel Ca2+-binding protein, p22, is required for constitutive membrane traffic.
We have identified a novel protein, p22, required for "constitutive" exocytic membrane traffic. p22 belongs to the EF-hand superfamily of Ca2+-binding proteins and shows extensive similarity to the regulatory subunit of protein phosphatase 2B, calcineurin B. p22 is a cytosolic N-myristoylated protein that undergoes conformational changes upon binding of Ca2+. Antibodies against a p22 peptide block the targeting/fusion of transcytotic vesicles with the apical plasma membrane, but recombinant wild-type p22 overcomes that inhibition. Nonmyristoylated p22, or p22 incapable of undergoing Ca2+-induced conformational changes, cannot reverse the antibody-mediated inhibition. The data suggest that p22 may act by transducing cellular Ca2+ signals to downstream effectors. p22 is ubiquitously expressed, and we propose that its function is required for membrane trafficking events common to many cells.
Barroso
M R
MR
Department of Cell Biology, University of Alabama Medical Center, Birmingham, Alabama 35294, USA.
Bernd
K K
KK
DeWitt
N D
ND
Chang
A
A
Mills
K
K
Sztul
E S
ES
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000378:metabolism* / Q000502:physiology*; D005089:Exocytosis; D015870:Gene Expression; D018257:Helix-Loop-Helix Motifs; D008074:Lipoproteins / Q000502:physiology*; D008561:Membrane Fusion; D008969:Molecular Sequence Data; D019814:Myristic Acid; D009227:Myristic Acids / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D002135:Calcium-Binding Proteins; D008074:Lipoproteins; D009227:Myristic Acids; D012333:RNA, Messenger; C098929:calcium binding protein p22, rat; D019814:Myristic Acid; D002118:Calcium