CNR - Institute of Neuroscience CNR
Institute of Neuroscience
 

Project

Role of the cytoskeleton and motor proteins during immune responses in autoimmune diseases

Microtubules are dynamic polymers made up of tubulin subunits. They provide architectural support for eukaryotic cells, and act as railways along which cytoplasmic constituents are actively transported. Kinesins (KIFs) are microtubule-based molecular motors which belong to the very large and conserved superfamily of ATPases involved in the anterograde transport of intracellular orgenelles. During mitosis and meiosis, KIFs are also involved in spindle organization and chromosome movements. In neurons, KIFs are essential for the anterograde transport of various molecules from the cell body to axons and dendrites, while cytoplasmic dyneins are minus-end-directed microtubule motors that transport cargoes from axonal or dendritic terminals to the cell body.

One of the plus-end-directed microtubule motors, KIF4, was originally characterized as a mitotic motor implicated in chromosome segregation during mitosis. However, it has been reported as highly expressed in the developing nervous system and to co-localize with membrane organelles. It seems that KIF4 plays a role in the microtubule-based transport of vesicles containing L1, a cell adhesion molecule, towards the tip of growth cones in developing neurons in culture.

KIF4 is absent or present at very low levels in most adult tissues, the notable exception being hematopoietic tissues where KIF4 is abundantly transcribed and synthesized. The Xenopus protein Xklp1, homolog of human KIF4, is involved in chromosome segregation during mitosis, however it has recently been proposed to be involved in the regulation of microtubule dynamics.

Accumulating data on KIF4 location in adults and a possible role in microtubule dynamics suggested to us that it might be involved at certain stages of immune cell activation and/or proliferation. It is known that F-actin and actin-associated proteins are involved in establishing the interaction between the effector T cell and the target cell, but the detailed molecular mechanisms involved in the reorientation of the microtubule cytoskeleton and microtubule-based movement of the microtubule-organizing center to a point on or close to the cell surface, and the detachment of secretory lysosomes from the microtubules with subsequent docking to the lymphocyte membrane during maturation of the immunological synapse, are poorly understood. By analogy with other systems, these processes are likely to require tight regulation of microtubule dynamics, involving the concerted action of various microtubule-stabilizing and/or destabilizing proteins as well as microtubule-based molecular motors.

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of subacute/chronic muscle disorders characterized by inflammation-mediated muscle degeneration. The major forms of IIM are dermatomyositis (DM), polymyositis (PM) and sporadic inclusion body myositis (IBM). Evidences for a primary autoimmune pathogenesis in PM and DM are muscle damage at the endomysium (infiltrating T cells in PM, complement-mediated humoral attack against endothelial cells in DM); frequent association with other autoimmune diseases; serum positivity for autoantibodies (e.g. anti-synthetase antibodies); and positive response to immunosoppressive treatments. In sporadic IBM, it is still unclear whether the immune response is primary or secondary. Triggering factors of myositis as well as the processes by which the immunological attack induces muscle weakness are still unknown.

 

In collaboration with the Laboratory of Neuromuscular Diseases of the Fondazione Istituto Neurologico "C. Besta" we investigated the possible involvement of KIF proteins in immune cell activation by characterizing the expression of KIF4 and other kinesin motors in muscle biopsies from patients with idiopathic inflammatory myopathy and in vitro during the activation steps of PBLs from healthy donors. Using different experimental approaches, such as Real-Time Quantitative PCR and immunohistochemistry, we found that the expression of KIF4 transcript is specifically upregulated in IIM muscle tissue compared to control and that KIF4 protein localizes in IIM muscle-infiltrating immune cells, preferably in association with CD3+ T lymphocytes near individual muscle fibers (Fig. 1). In vitro analysis of KIF4 mRNA levels in peripheral blood lymphocytes (PBLs) obtained from healthy donors and activated with various stimuli, revealed that upregulation of KIF4 transcript correlates with cell activation and proliferation; moreover, immunofluorescence analysis of the intracellular distribution of KIF4 protein in PBLs indicated that this kinesin motor colocalizes in the cytoplasm with lytic granules. These results represent the first observation that KIF4 is present in the muscle of patients with IIM as well as in activated PBLs in vitro and suggest that KIF4 may be involved in the cytoskeleton modifications associated with cell activation. More importantly, they lead the way to further studies aimed at the elucidation of the full biological role of this kinesin motor in inflammatory processes.

Publications

  • Bernasconi P, Cappelletti C, Navone F, Nessi V, Baggi F, Vernos I, Romaggi S, Confalonieri P, Mora M, Morandi L, Mantegazza R (2008) The kinesin superfamily motor protein KIF4 is associated with immune cell activation in idiopathic inflammatory myopathies. J. Neuropathol. Exp. Neurol. 67:624-32.

Grants

Fondazione Monte dei Paschi di Siena

Collaborations

  • P. Bernasconi, R. Mantegazza, Fondazione Istituto Neurologico "C. Besta", Milan, Italy.
  • I. Vernos, Centro de Regulacion Genomica, Cell and Developmental Biology Program, Barcelona, Spain.

 

PI photo

Francesca Navone

Contact information

email  E-mail

email  +39 02 5031 6968

Participating staff
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