Megalencephalic leukoencephalopathy with subcortical cysts protein-1: A new calcium-sensitive protein functionally activated by endoplasmic reticulum calcium release and calmodulin binding in astrocytes.

BACKGROUND: MLC1 is a membrane protein highly expressed in brain perivascular astrocytes and whose mutations account for the rare leukodystrophy (LD) megalencephalic leukoencephalopathy with subcortical cysts disease (MLC). MLC is characterized by macrocephaly, brain edema and cysts, myelin vacuolation and astrocyte swelling which cause cognitive and motor dysfunctions and epilepsy. In cultured astrocytes, lack of functional MLC1 disturbs cell volume regulation by affecting anion channel (VRAC) currents and the consequent regulatory volume decrease (RVD) occurring in response to osmotic changes. Moreover, MLC1 represses intracellular signaling molecules (EGFR, ERK1/2, NF-kB) inducing astrocyte activation and swelling following brain insults. Nevertheless, to date, MLC1 proper function and MLC molecular pathogenesis are still elusive. We recently reported that in astrocytes MLC1 phosphorylation by the Ca2+/Calmodulin-dependent kinase II (CaMKII) in response to intracellular Ca2+ release potentiates MLC1 activation of VRAC. These results highlighted the importance of Ca2+ signaling in the regulation of MLC1 functions, prompting us to further investigate the relationships between intracellular Ca2+ and MLC1 properties. METHODS: We used U251 astrocytoma cells stably expressing wild-type (WT) or mutated MLC1, primary mouse astrocytes and mouse brain tissue, and applied biochemistry, molecular biology, video imaging and electrophysiology techniques. RESULTS: We revealed that WT but not mutant MLC1 oligomerization and trafficking to the astrocyte plasma membrane is favored by Ca2+ release from endoplasmic reticulum (ER) but not by capacitive Ca2+ entry in response to ER depletion. We also clarified the molecular events underlining MLC1 response to cytoplasmic Ca2+ increase, demonstrating that, following Ca2+ release, MLC1 binds the Ca2+ effector protein calmodulin (CaM) at the carboxyl terminal where a CaM binding sequence was identified. Using a CaM inhibitor and generating U251 cells expressing MLC1 with CaM binding site mutations, we found that CaM regulates MLC1 assembly, trafficking and function, being RVD and MLC-linked signaling molecules abnormally regulated in these latter cells. CONCLUSION: Overall, we qualified MLC1 as a Ca2+ sensitive protein involved in the control of volume changes in response to ER Ca2+ release and astrocyte activation. These findings provide new insights for the comprehension of the molecular mechanisms responsible for the myelin degeneration occurring in MLC and other LD where astrocytes have a primary role in the pathological process.

[Prescription guidebook for temozolomide usage in brain tumors]. / Guide de prescription et de bon usage du témozolomide dans les tumeurs cérébrales.

Malignant gliomas are the most frequent primary brain tumors in adults. Temozolomide is an oral alkylating cytotoxic agent of second generation, used in the treatment of high-grade gliomas. It is indicated in newly diagnosed glioblastoma multiform as well as in recurrent or progressive malignant gliomas, such as glioblastoma multiform or anaplastic astrocytoma. However, temozolomide is also used, off label, in other clinical situations and the main objective of this study was to establish recommendations and guidelines for relevant prescriptions of temozolomide in primary brain tumors and brain metastasis in adults. The literature review was analysed by experts who determined the evidence level (A to E) according to the scale of recommendations adopted by the "Haute Autorité de santé--HAS--(French National Authority for Health)". For high-grade and low-grade gliomas, based on the level of evidence from the literature, the use of temozolomide can be justified, with a B2 score attributed to these indications. In contrast, for the others indications, the use of temozolomide appeared to be more controversial or even not recommended (score C to E). Regarding the dosing schedule and administration scheme, as well as the co-administration with other anticancer drugs, a C score was attributed for the off label situations.

Protein S deficiency. Description of a case associated with chronic inflammatory bowel disease.

Thrombotic disease is one of the most relevant clinical problems for morbility and mortality. We can differentiate congenital and acquired forms. In this short communication we describe 1 case observed by us that seems interesting for the association of a congenital and acquired form [Protein S deficiency and inflammatory bowel disease (IBD)] and for the dramatic events suffered before receiving a complete diagnosis and therapy, indicating the importance of recollection of information from the patients, starting from anamnestic data.