ABSTRACT
Mutations in the ACTN4 gene, encoding the actin crosslinking protein alpha-actinin-4, are associated with a familial form of focal segmental glomerulosclerosis (FSGS). Mice with podocyte-specific expression of K256E alpha-actinin-4 develop foot process effacement and glomerulosclerosis, highlighting the importance of the cytoskeleton in podocyte structure and function. K256E alpha-actinin-4 exhibits increased affinity for F-actin. However, the downstream effects of this aberrant binding on podocyte dynamics remain unclear. Wild-type and K256E alpha-actinin-4 were expressed in cultured podocytes via adenoviral infection to determine the effect of the mutation on alpha-actinin-4 subcellular localization and on cytoskeletal-dependent processes such as adhesion, spreading, migration, and formation of foot process-like peripheral projections. Wild-type alpha-actinin-4 was detected primarily in the Triton-soluble fraction of podocyte lysates and localized to membrane-associated cortical actin and focal adhesions, with some expression along stress fibers. Conversely, K256E alpha-actinin-4 was detected predominantly in the Triton-insoluble fraction, was excluded from cortical actin, and localized almost exclusively along stress fibers. Both wild-type and K256E alpha-actinin-4-expressing podocytes adhered equally to an extracellular matrix (collagen-I). However, podocytes expressing K256E alpha-actinin-4 showed a reduced ability to spread and migrate on collagen-I. Lastly, K256E alpha-actinin-4 expression reduced the mean number of actin-rich peripheral projections. Our data suggest that aberrant sequestering of K256E alpha-actinin-4 impairs podocyte spreading, motility, and reduces the number of peripheral projections. Such intrinsic cytoskeletal derangements may underlie initial podocyte damage and foot process effacement encountered in ACTN4-associated FSGS.
Subject(s)
Actinin/genetics , Cytoskeleton/pathology , Glomerulosclerosis, Focal Segmental/genetics , Glomerulosclerosis, Focal Segmental/physiopathology , Podocytes/pathology , Actinin/metabolism , Adenoviridae/genetics , Animals , Cell Adhesion/genetics , Cell Line, Transformed , Cell Movement/genetics , Cell Transformation, Viral , Disease Models, Animal , Gene Expression , Glomerulosclerosis, Focal Segmental/pathology , MiceABSTRACT
Glucose monitoring is a widely-used procedure in caring for critically ill patients. The determination of a blood glucose using arterial blood has not been approved with the use of glucose meters. After comparing the data from 75 subjects using the parameters established by the American Diabetes Association, arterial blood proved to be an accurate indicator of a subject's blood glucose level. The benefits enjoyed by both the patients and nursing staff establish a convincing reason to incorporate this procedure into current nursing practice. This article will describe the sample, method and results used to affect change in clinical practice.
