Ninein isoform contributions to intracellular processes and macrophage immune function

Area of Science:

• Cell Biology
• Molecular Biology
• Immunology

Background:

• Ninein is a key protein regulating microtubule organization and dynein/dynactin complex activity.
• Multiple ninein isoforms exist, but their specific functions and contributions remain unclear.

Purpose of the Study:

• To identify and characterize distinct ninein isoforms in mouse macrophages.
• To elucidate the specific intracellular and functional roles of ninein^CAN and ninein^ISO2 in macrophages.

Main Methods:

• Identification of two ninein isoforms (ninein^CAN and ninein^ISO2) with distinct C-termini and expression levels.
• Analysis of pre-mRNA splicing events.
• Selective and total protein knockdown experiments combined with live cell imaging and microscopy.

Main Results:

• Both ninein isoforms are involved in cell proliferation and microtubule nucleation/centrosome integrity.
• Ninein^CAN, but not ninein^ISO2, is crucial for centrosome separation and dynein-dependent Golgi positioning.
• Ninein^ISO2 primarily mediates F-actin recruitment for particle internalization, while both are needed for dynein/dynactin recruitment.

Conclusions:

• Alternative splicing generates ninein isoforms with both overlapping and unique functions in macrophages.
• Differential roles of ninein isoforms impact microtubule organization, organelle positioning, and macrophage phagocytic function.