TY - JOUR
T1 - Bax inhibitor 1 increases cell adhesion through actin polymerization
T2 - Involvement of calcium and actin binding
AU - Lee, Geum Hwa
AU - Ahn, Taeho
AU - Kim, Do Sung
AU - Park, Seoung Ju
AU - Lee, Yong Chul
AU - Yoo, Wan Hee
AU - Jung, Sung Jun
AU - Yang, Jae Seong
AU - Kim, Sanguk
AU - Muhlrad, Andras
AU - Seo, Young Rok
AU - Chae, Soo Wan
AU - Kim, Hyung Ryong
AU - Chae, Han Jung
PY - 2010/4
Y1 - 2010/4
N2 - Bax inhibitor 1 (BI-1), a transmembrane protein with Ca2+ channel-like activity, has antiapoptotic and anticancer activities. Cells overexpressing BI-1 demonstrated increased cell adhesion. Using a proteomics tool, we found that BI-1 interacted with γ-actin via leucines 221 and 225 and could control actin polymerization and cell adhesion. Among BI-1 -/- cells and cells transfected with BI-1 small interfering RNA (siRNA), levels of actin polymerization and cell adhesion were lower than those among BI-1+/+ cells and cells transfected with nonspecific siRNA. BI-1 acts as a leaky Ca2+ channel, but mutations of the actin binding sites (L221A, L225A, and L221A/L225A) did not change intra-endoplasmic reticulum Ca2+, although deleting the C-terminal motif (EKDKKKEKK) did. However, store-operated Ca2+ entry (SOCE) is activated in cells expressing BI-1 but not in cells expressing actin binding site mutants, even those with the intact C-terminal motif. Consistently, actin polymerization and cell adhesion were inhibited among all the mutant cells. Compared to BI-1 +/+ cells, BI-1-/- cells inhibited SOCE, actin polymerization, and cell adhesion. Endogenous BI-1 knockdown cells showed a similar pattern. The C-terminal peptide of BI-1 (LMMLILAMNRKDKKKEKK) polymerized actin even after the deletion of four or six charged C-terminal residues. This indicates that the actin binding site containing L221 to D231 of BI-1 is responsible for actin interaction and that the C-terminal motif has only a supporting role. The intact C-terminal peptide also bundled actin and increased cell adhesion. The results of experiments with whole recombinant BI-1 reconstituted in membranes also coincide well with the results obtained with peptides. In summary, BI-1 increased actin polymerization and cell adhesion through Ca2+ regulation and actin interaction.
AB - Bax inhibitor 1 (BI-1), a transmembrane protein with Ca2+ channel-like activity, has antiapoptotic and anticancer activities. Cells overexpressing BI-1 demonstrated increased cell adhesion. Using a proteomics tool, we found that BI-1 interacted with γ-actin via leucines 221 and 225 and could control actin polymerization and cell adhesion. Among BI-1 -/- cells and cells transfected with BI-1 small interfering RNA (siRNA), levels of actin polymerization and cell adhesion were lower than those among BI-1+/+ cells and cells transfected with nonspecific siRNA. BI-1 acts as a leaky Ca2+ channel, but mutations of the actin binding sites (L221A, L225A, and L221A/L225A) did not change intra-endoplasmic reticulum Ca2+, although deleting the C-terminal motif (EKDKKKEKK) did. However, store-operated Ca2+ entry (SOCE) is activated in cells expressing BI-1 but not in cells expressing actin binding site mutants, even those with the intact C-terminal motif. Consistently, actin polymerization and cell adhesion were inhibited among all the mutant cells. Compared to BI-1 +/+ cells, BI-1-/- cells inhibited SOCE, actin polymerization, and cell adhesion. Endogenous BI-1 knockdown cells showed a similar pattern. The C-terminal peptide of BI-1 (LMMLILAMNRKDKKKEKK) polymerized actin even after the deletion of four or six charged C-terminal residues. This indicates that the actin binding site containing L221 to D231 of BI-1 is responsible for actin interaction and that the C-terminal motif has only a supporting role. The intact C-terminal peptide also bundled actin and increased cell adhesion. The results of experiments with whole recombinant BI-1 reconstituted in membranes also coincide well with the results obtained with peptides. In summary, BI-1 increased actin polymerization and cell adhesion through Ca2+ regulation and actin interaction.
UR - http://www.scopus.com/inward/record.url?scp=77949355135&partnerID=8YFLogxK
U2 - 10.1128/MCB.01357-09
DO - 10.1128/MCB.01357-09
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C2 - 20123969
AN - SCOPUS:77949355135
SN - 0270-7306
VL - 30
SP - 1800
EP - 1813
JO - Molecular and Cellular Biology
JF - Molecular and Cellular Biology
IS - 7
ER -