Integrin signalling defects in T-lymphocytes in systemic lupus erythematosus

The role of protein kinase C isoenzymes in the pathogenesis of human autoimmune diseases

The physiological role of protein kinase C (PKC) enzymes in the immune system is presented briefly. From earlier publications of others data were collected how the defects of one/two isoenzymes of PKC system suggested their involvement in the pathogenesis of human autoimmune diseases. Our observations on the defects of seven PKC isoenzymes in the peripheral blood mononuclear cells (PBMC) demonstrate that these molecular impairments are not prerequisits of the pathogenesis of systemic lupus erythematosus (SLE), mixed connective tissue disease and Sjögren's syndrome. However, these defects can modulate the disease activity and symptoms especially in SLE by several pathways. The role of PKC system in other forms of autoimmune diseases is also very small. It was of note that we detected decreased expression of PKC isoenzymes in PBMC of a European white family with an X-linked genetic background showing seasonal undulations in the lupus patient and also in her healthy mother.

Integrating receptor signal inputs that influence small Rho GTPase activation dynamics at the immunological synapse

The Rho GTPase Cdc42 regulates cytoskeletal changes at the immunological synapse (IS) that are critical to T-cell activation. By imaging fluorescent activity biosensors (Raichu) using fluorescence lifetime imaging microscopy, Cdc42 activation was shown to display kinetics that are conditional on the specific receptor input (through two IS-associated receptors, CD3 and beta1 integrin). CD3-triggered Cdc42 activity is dependent on the cyto-2 (NPIY) motif of the beta1 integrin cytoplasmic domain. Perturbations of the ezrin-radixin-moesin (ERM) function blocked CD3- and beta1-dependent increases in Cdc42 activity. Both IS-associated receptors probably lie on a serial molecular pathway and transduce signals through the ERM-dependent machinery that is responsible for the remodeling and stabilization of the synapse. Cdc42 activity is impaired in beta1 integrin-deficient T cells that form conjugates with antigen-presenting cells but is partially restored in the context of an antigen-specific synapse. This restoration of Cdc42 activity is due, at least in part, to the recruitment and activation of beta2 integrin.

Altered T and B lymphocyte signaling pathways in lupus

Systemic lupus erythematosus (SLE) has long been recognized to be characterized by dysregulated signaling pathways in T and B lymphocytes, beginning with observations of cellular hyperactivity and hyperresponsiveness, and evolving to recent studies focused upon the genetic and molecular bases of such phenomena. This review focuses on recently elucidated signaling abnormalities currently thought to be intrinsic to T and/or B cells in human SLE.

Uncovering the genetics of systemic lupus erythematosus: implications for therapy

Although it is well known that genetic factors contribute significantly to the expression of systemic lupus erythematosus (SLE) it was only recently realized, through genome-wide searches, that the number of involved genes is rather large. The published information hints at two facts: first, the number of genomic loci identified in various diverse cohorts is large and not necessarily overlapping; and second, certain loci may be preferentially linked with specific clinical manifestations. The latter may ultimately lead to a better understanding of the nature of the clinical entity that we know as SLE, and identification of groups of patients prone to respond better to treatment or to develop significant adverse effects. Advances attained regarding the nature of the biochemical and molecular defects that underwrite the aberrant function of immune cells parallel the progress made on the genetic origin of the disease. The genetic links need to be connected with aberrant function of their products to validate their significance. It is expected that correction of molecular aberrations either medicinally or by gene therapy will provide the needed specific treatment for patients with SLE.