CD45 engagement induces L-selectin down-regulation

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• CD45 glycoprotein isoforms possess intracellular protein tyrosine phosphatase (PTPase) activity.
• L-selectin (CD62L) is a crucial leukocyte glycoprotein involved in cell adhesion and migration.
• The precise regulatory mechanisms of L-selectin expression remain incompletely understood.

Purpose of the Study:

• To investigate the role of CD45 in the regulation of L-selectin (CD62L) surface expression on lymphocytes and granulocytes.
• To elucidate the involvement of PTPase activity, protein tyrosine kinase (PTK) signaling, and protein kinase C (PKC) in CD45-mediated L-selectin regulation.

Main Methods:

• Utilized monoclonal antibodies (MoAbs) targeting CD45 epitopes.
• Employed chemical inhibitors including herbimycin A (PTK inhibitor) and H 7 (PKC inhibitor).
• Used vanadate as a PTPase inhibitor and phorbol 12-myristate 13-acetate (PMA) for PKC activation.

Main Results:

• Anti-CD45 MoAbs induced L-selectin down-regulation on lymphocytes, enhanced by cell density and partially inhibited by herbimycin A.
• Vanadate, a CD45 PTPase inhibitor, induced L-selectin down-regulation on both lymphocytes and granulocytes.
• PMA and H 7 modulated L-selectin expression, with synergistic or antagonistic effects observed with vanadate depending on cell type.

Conclusions:

• CD45 plays a significant role in regulating L-selectin surface expression in a cell type-specific manner.
• Tyrosine phosphorylation/dephosphorylation cascades and the PKC system are key components in the regulation of L-selectin.
• These findings contribute to understanding leukocyte adhesion and immune cell trafficking.