CaV1.1 Calcium Channel Signaling Complexes in Excitation-Contraction Coupling: Insights from Channelopathies.

In skeletal muscle, excitation-contraction (EC) coupling relies on the mechanical coupling between two ion channels: the L-type voltage-gated calcium channel (CaV1.1), located in the sarcolemma and functioning as the voltage sensor of EC coupling, and the ryanodine receptor 1 (RyR1), located on the sarcoplasmic reticulum serving as the calcium release channel. To this day, the molecular mechanism by which these two ion channels are linked remains elusive. However, recently, skeletal muscle EC coupling could be reconstituted in heterologous cells, revealing that only four proteins are essential for this process: CaV1.1, RyR1, and the cytosolic proteins CaVß1a and STAC3. Due to the crucial role of these proteins in skeletal muscle EC coupling, any mutation that affects any one of these proteins can have devastating consequences, resulting in congenital myopathies and other pathologies.Here, we summarize the current knowledge concerning these four essential proteins and discuss the pathophysiology of the CaV1.1, RyR1, and STAC3-related skeletal muscle diseases with an emphasis on the molecular mechanisms. Being part of the same signalosome, mutations in different proteins often result in congenital myopathies with similar symptoms or even in the same disease.

STAC3 determines the slow activation kinetics of CaV 1.1 currents and inhibits its voltage-dependent inactivation.

The skeletal muscle CaV 1.1 channel functions as the voltage-sensor of excitation-contraction (EC) coupling. Recently, the adaptor protein STAC3 was found to be essential for both CaV 1.1 functional expression and EC coupling. Interestingly, STAC proteins were also reported to inhibit calcium-dependent inactivation (CDI) of L-type calcium channels (LTCC), an important negative feedback mechanism in calcium signaling. The same could not be demonstrated for CaV 1.1, as STAC3 is required for its functional expression. However, upon strong membrane depolarization, CaV 1.1 conducts calcium currents characterized by very slow kinetics of activation and inactivation. Therefore, we hypothesized that the negligible inactivation observed in CaV 1.1 currents reflects the inhibitory effect of STAC3. Here, we inserted a triple mutation in the linker region of STAC3 (ETLAAA), as the analogous mutation abolished the inhibitory effect of STAC2 on CDI of CaV 1.3 currents. When coexpressed in CaV 1.1/STAC3 double knockout myotubes, the mutant STAC3-ETLAAA failed to colocalize with CaV 1.1 in the sarcoplasmic reticulum/membrane junctions. However, combined patch-clamp and calcium recording experiments revealed that STAC3-ETLAAA supports CaV 1.1 functional expression and EC coupling, although at a reduced extent compared to wild-type STAC3. Importantly, STAC3-ETLAAA coexpression dramatically accelerated the kinetics of activation and inactivation of CaV 1.1 currents, suggesting that STAC3 determines the slow CaV 1.1 currents kinetics. To examine if STAC3 specifically inhibits the CDI of CaV 1.1 currents, we performed patch-clamp recordings using calcium and barium as charge carriers in HEK cells. While CaV 1.1 displayed negligible CDI with STAC3, this did not increase in the presence of STAC3-ETLAAA. On the contrary, our data demonstrate that STAC3 specifically inhibits the voltage-dependent inactivation (VDI) of CaV 1.1 currents. Altogether, these results designate STAC3 as a crucial determinant for the slow activation kinetics of CaV 1.1 currents and implicate STAC proteins as modulators of both components of inactivation of LTCC.

Efficacy of intensive hand physical therapy in patients with systemic sclerosis.

OBJECTIVES: To evaluate the efficacy of a three-week period of complex and intensive hand physical therapy on hand function in patients with systemic sclerosis (SSc). METHODS: Thirty-one patients with SSc were treated. Hand stretching exercises, ergotherapy supplemented with thermal and mud baths, whirlpool therapy and soft tissue massage were daily used during a three-week period. The control SSc group (n=22) received similar management for their large joints leaving out their hands. The primary outcomes of this study were the Health Assessment Questionnaire (HAQ) and the Disabilities of the Arm, Shoulder and Hand (DASH). Hand Anatomic Index (HAI), Cochin Hand Function (CHFT) and clinical characteristics were also assessed before starting the therapy and six months afterwards. RESULTS: Six months after the investigation period, only the group receiving hand physical therapy showed improvement in HAQ and DASH scores compared to the baseline values (p<0.05). The improvement in median HAQ value (25%-75% quartiles) reached the clinical meaningful rate (baseline 1.125/0.625-1.625/ versus 0.75/0.25-1.5/ at six months). Visual analogue scales of global pain (p<0.01) and Raynaud's phenomenon (p<0.05) also had better results than at baseline. HAI, gripping strength and CHFT also showed some improvement, but did not reach the significance level of change by the end of the six-month observation period. CONCLUSIONS: The complex physical therapy caused favourable changes in both the HAQ and the DASH indicating that this particular program had some long-term beneficial effect on hand function in patients with SSc.

[Use of angioneogenesis inhibitor monoclonal antibody following standard therapy in recurrent or progressive glioblastoma multiforme]. / Érújdonképzodés-gátló monoklonális antitest alkalmazása a szokásos kezelést követoen kiújuló vagy progrediáló glioblastoma multiforme kezelésében.

Glioblastoma is a brain tumor with poor prognosis in the therapy of which operation, postoperative temozolomide sensitized radiochemotherapy followed by temozolomide monotherapy offer the best chances. Administration of temozolomide is also recommended in relapse if the patient is naïve to this treatment. In recurrent or progressive glioblastoma following the above therapy, several biological therapeutic agents were tested, out of which the angiogenesis inhibitor bevacizumab has been approved by FDA (and similar authority of several other countries). Bevacizumab monotherapy resulted in objective tumor response in 28.2%, the median of progression-free survival was 4.2 (2.9-5.8) months, the median of overall survival was 9.2 (8.2-10.7) months. When combined with irinotecan, these results were 37.8%, 5.6 (4.4-6.2) and 8.7 (7.8-10.9) months, respectively. Adverse events were known from the use of bevacizumab in other indications, symptoms affecting the central nervous system were mild, i.e. the therapy proved to be not only effective but safe as well. Reduction of edema provided further advantage. In Hungary the product is available for "off-label" use only through a fairness request process.

Proteomic and toxicological analysis of the venom of Micrurus yatesi and its neutralization by an antivenom.

Coralsnakes belong to the family Elapidae and possess venoms which are lethal to humans and can be grouped based on the predominance of either three finger toxins (3FTxs) or phospholipases A2 (PLA2s). A proteomic and toxicological analysis of the venom of the coralsnake Micrurus yatesi was performed. This species, distributed in southeastern Costa Rica, was formerly considered a subspecies of M. alleni. Results showed that this venom is PLA2-rich, in contrast with the previously studied venom of Micrurus alleni. Toxicological evaluation of the venom, in accordance with proteomic data, revealed that it has a markedly higher in vitro PLA2 activity upon a synthetic substrate than M. alleni. The evaluation of in vivo myotoxicity in CD-1 mice using histological evaluation and plasma creatine kinase release also showed that M. yatesi venom caused muscle damage. A commercial equine antivenom prepared using the venom of Micrurus nigrocinctus displayed a similar recognition of the venoms of M. yatesi and M. nigrocinctus by enzyme immunoassay. This antivenom also immunorecognized the main fractions of the venom of M. yatesi and was able to neutralize its lethal effect in a murine model.

[Detection of multiple colon and rectal tumors during diagnostic treatment and follow-up]. / Többszörös vastag- és végbéldaganatok felismerése a kivizsgálás, kezelés és gondozás során.

Recognition of the commonly encountered colorectal cancer (CRC) generally begins and takes place because of and based on symptoms and signs, due to the unsettled screening of this type of cancer. Sometimes, because of advanced stage cancer urgent surgical intervention could become necessary and, if this is the case, there is no time and possibility for searching for an eventual second tumor and perhaps the patient's status does not permit performing intraoperative investigations either. The incidence of multiple colon cancer is considered to be between 2.5 and 30% according to the literature. That is why one should exclude them even in the absence of pre- and intraoperative investigations and complaints. On the other hand, colonoscopy and perhaps irrigoscopy of seemingly healthy followed-up patients is mandatory. In the case of the presence of complaints/symptoms denoting impaired intestinal passage seen in a followed-up patient or during the adjuvant setting or metastatic/recurrent disease, treatment and even during hospice care we should evaluate the possibility of a second metachronous tumor. Moreover, if there is no urgency, the multidisciplinary team (oncoteam) should recommend the adequate treatment by balancing gain/utility and risk.