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Related Experiment Video

Updated: May 14, 2026

"Phagosome Closure Assay" to Visualize Phagosome Formation in Three Dimensions Using Total Internal Reflection Fluorescent Microscopy (TIRFM)

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Published on: August 26, 2016

RIAM (Rap1-interacting adaptor molecule) regulates complement-dependent phagocytosis.

Iria Medraño-Fernandez¹, Raquel Reyes, Isabel Olazabal

¹Departamento de Microbiología I, Inmunología, Facultad de Medicina, Universidad Complutense de Madrid, 28040 Madrid, Spain.

Cellular and Molecular Life Sciences : CMLS

|February 20, 2013

Summary

RIAM is essential for complement-mediated phagocytosis by recruiting talin to the CR3 receptor, a process regulated by Rap1 activation. This pathway is crucial for immune cell function.

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Last Updated: May 14, 2026

"Phagosome Closure Assay" to Visualize Phagosome Formation in Three Dimensions Using Total Internal Reflection Fluorescent Microscopy (TIRFM)

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Identification of Inositol Phosphate or Phosphoinositide Interacting Proteins by Affinity Chromatography Coupled to Western Blot or Mass Spectrometry

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Published on: July 26, 2019

Area of Science:

Immunology
Cell Biology
Molecular Mechanisms

Background:

Phagocytosis via complement receptor CR3 (integrin αMß2) involves talin recruitment to the ß2 integrin subunit.
Talin recruitment is Rap1-dependent, but the precise regulatory mechanism is unclear.

Purpose of the Study:

To investigate the role of Rap1 effector RIAM in regulating complement-mediated phagocytosis.
To elucidate the mechanism by which Rap1 influences CR3-dependent phagocytosis.

Main Methods:

Utilized human myeloid cell lines (HL-60, THP-1) and primary monocyte-derived macrophages.
Employed RIAM knockdown strategies and Rap1 activation via EPAC.
Assessed integrin affinity changes, phagocytosis of opsonized particles, and talin recruitment.

Main Results:

RIAM knockdown impaired αMß2 integrin affinity changes and complement-opsonized particle phagocytosis.
Rap1 activation enhanced complement-mediated phagocytosis, an effect dependent on RIAM.
Talin recruitment to ß2 integrin during phagocytosis was reduced in RIAM-deficient cells.

Conclusions:

RIAM acts as a critical downstream effector of Rap1 in the phagocytosis pathway.
RIAM mediates its function by recruiting talin to complement receptors, facilitating CR3-mediated phagocytosis.