Spectrin-like proteins are found in a wide variety of non-erythroid cells where they generally occur in the cell cortex near the plasma membrane. To determine the intracellular distribution of alpha-spectrin (alpha-fodrin) in lymphocytes, we have developed an immunoperoxidase method to localize this protein at the ultrastructural level. Of considerable interest, particularly with regard to our efforts to determine the function of spectrin in this cell type, was the finding that its subcellular localization and its relationship with the plasma membrane can vary dramatically. Based on its position in the cell, alpha-spectrin can occur in two forms in lymphocytes: one that associates closely with the plasma membrane and another that occurs at some distance from the cell periphery, either as a single large aggregate or as several smaller ones. The single large aggregate of spectrin is a stable feature in a number of lymphocyte cell lines and hybrids which were used to examine its ultrastructural characteristics. A previously undescribed cellular structure, consisting of a meshwork of spectrin filaments and membranous vesicles, was identified in these cells. This structure could be induced to dissipate in response to membrane perturbants (e.g., hyperthermia and phorbol esters, known effectors of lymphocyte function and differentiation) and the patterns resulting from the redistribution of spectrin were a reflection of those observed routinely in lymphocytes in situ. The correlation between naturally occurring spectrin localization patterns and those seen after membrane perturbation suggested the possibility that spectrin distribution is indicative of particular maturation stages or functional states in lymphocytes. The implications of these findings with regard to the role of spectrin in lymphocyte function are discussed.

EPB41

10.1083/jcb.106.1.97

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Citations (86)

Dynamic Association of L-Selectin with the Lymphocyte Cytoskeletal Matrix

The Journal of Immunology (1999)

Sharon S. Evans David M. Schleider Lori A. Bowman Michelle L. Francis Geoffrey S. Kansas

L-selectin mediates lymphocyte extravasation into lymphoid tissues through binding to sialomucin-like receptors on the surface of high endothelial venules (HEV). This study examines the biochemical basis and regulation of interactions between L-selectin, an integral transmembrane protein, and the lymphocyte cytoskeleton. Using a detergent-based extraction procedure, constitutive associations between L-selectin and the insoluble cytoskeletal matrix could not be detected. However, engagement of the L-selectin lectin domain by Abs or by glycosylation-dependent cell adhesion molecule-1, an HEV-derived ligand for L-selectin, rapidly triggered redistribution of L-selectin to the detergent-insoluble cytoskeleton. L-selectin attachment to the cytoskeleton was not prevented by inhibitors of actin/microtubule polymerization (cytochalasin B, colchicine, or nocodozole) or serine/threonine and tyrosine kinase activity (staurosporine, calphostin C, or genistein), although L-selectin-mediated adhesion of human PBL was markedly suppressed by these agents. Exposure of human PBL or murine pre-B transfectants expressing full-length human L-selectin to fever-range hyperthermia also markedly increased L-selectin association with the cytoskeleton, directly correlating with enhanced L-selectin-mediated adhesion. In contrast, a deletion mutant of L-selectin lacking the COOH-terminal 11 amino acids failed to associate with the cytoskeletal matrix in response to Ab cross-linking or hyperthermia stimulation and did not support adhesion to HEV. These studies, when taken together with the previously demonstrated interaction between the L-selectin cytoplasmic domain and the cytoskeletal linker protein alpha-actinin, strongly implicate the actin-based cytoskeleton in dynamically controlling L-selectin adhesion.

10.4049/jimmunol.162.6.3615

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P468: 22q11DS with maternal mosaic nonoverlapping isodicentric 22q11 duplication

Genetics in Medicine Open (2024)

Zachary R. Spahr Jennifer D. Black Scott C. Smith Robert Roger Lebel

22q11.2 deletion syndrome (22q11DS) is a contiguous gene deletion syndrome characterized by highly variable adverse phenotypes which include craniofacial anomalies, cardiovascular malformations, immune deficiency, neonatal hypocalcemia, neurodevelopmental and psychiatric disorders. Low copy repeats (LCR) in the 22q region facilitate an increased rate of non-allelic homologous recombination, leading to deletions and duplications that are often de novo in origin. Genetic and epigenetic interactions between genes within the region (TBX1, DGCR8, CRKL, SNAP29) and across the genome result in incomplete penetrance and variable expressivity. Clinical presentations of identical deletions can be variable due to these interactions. We report a case of a 13 month old male born at 37 weeks to a 24-year-old G4P1021>2022 woman, with the pregnancy complicated by an enlarged urinary bladder and concomitant hydronephrosis. The newborn was found to have posterior urethral valves, moderate sized secundum ASD, microcephaly, truncal hypotonia, low-set ears, broad nasal bridge, anteverted nares, micrognathia, submucous cleft palate, left cryptorchidism and brisk patellar reflexes. Microarray revealed a 2.549 Mb deletion of 22q11.2 encompassing clusters A-D, which was confirmed with FISH. His mother's medical history is significant for polycystic ovary syndrome, hypoglycemia, mild aortic insufficiency, anxiety and depression; her microarray analysis showed a 2.03 Mb duplication/triplication of 22q11.1-q11.21 that does not overlap with her son's deletion, but rather encompasses the critical region for cat eye syndrome. Subsequent chromosome analysis showed a mosaic supernumerary isodicentric chromosome in 3 out of 5 cells (mos 47,XX,+idic (22)(q11.21)[3]/46,XX[2]). The proband's maternal half-sister had speech delay and suspected autism spectrum disorder, but microarray was negative. Extended family includes congenital heart defect and autism, but the affected persons have not had genetic workups. The 22q11 region is prone to deletions and duplications and is often altered in a de novo fashion. The son has a 2.549 Mb deletion of 22q11.2, while the mother has a mosaic supernumerary isodicentric chromosome 22q, but only a mild phenotypic presentation. Further family history of cardiac defects and autism spectrum disorder in maternal cousins raises the tempting possibility of 22q11 region alterations in three generations, but we lack documentation to support further consideration of the matter.

Mosaic

10.1016/j.gimo.2024.101362

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Protein Kinase Cα Signaling Regulates Inhibitor of DNA Binding 1 in the Intestinal Epithelium

Journal of Biological Chemistry (2011)

Fang Hao Marybeth A. Pysz Kathryn Curry Kristin N. Haas Steven J. Seedhouse

Increasing evidence supports a role for PKCα in growth arrest and tumor suppression in the intestinal epithelium. In contrast, the Id1 transcriptional repressor has pro-proliferative and tumorigenic properties in this tissue. Here, we identify Id1 as a novel target of PKCα signaling. Using a highly specific antibody and a combined morphological/biochemical approach, we establish that Id1 is a nuclear protein restricted to proliferating intestinal crypt cells. A relationship between PKCα and Id1 was supported by the demonstration that (a) down-regulation of Id1 at the crypt/villus junction coincides with PKCα activation, and (b) loss of PKCα in intestinal tumors is associated with increased levels of nuclear Id1. Manipulation of PKCα activity in IEC-18 nontransformed intestinal crypt cells determined that PKCα suppresses Id1 mRNA and protein via an Erk-dependent mechanism. PKCα, but not PKCδ, also inhibited Id1 expression in colon cancer cells. Id1 was found to regulate cyclin D1 levels in IEC-18 and colon cancer cells, pointing to a role for Id1 suppression in the antiproliferative/tumor suppressive activities of PKCα. Notably, Id1 expression was elevated in the intestinal epithelium of PKCα-knock-out mice, confirming that PKCα regulates Id1 in vivo. A wider role for PKCα in control of inhibitor of DNA binding factors is supported by its ability to down-regulate Id2 and Id3 in IEC-18 cells, although their suppression is more modest than that of Id1. This study provides the first demonstrated link between a specific PKC isozyme and inhibitor of DNA binding factors, and it points to a role for a PKCα → Erk ⊣ Id1 → cyclin D1 signaling axis in the maintenance of intestinal homeostasis.

Intestinal epithelium

10.1074/jbc.m110.208488

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P340: Kabuki syndrome and metachromatic leukodystrophy, dual diagnosis in a female patient: A case report

Genetics in Medicine Open (2023)

Margarita Vazquez Almonte Jennifer D. Black Melissa Byler Robert Roger Lebel Nienke P. Dosa

Kabuki

Kabuki syndrome

10.1016/j.gimo.2023.100368

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