The interaction of T-cell receptors (TCRs) with self- and non-self-peptides in the major histocompatibility complex (MHC) stimulates crucial signaling events, which in turn can activate T lymphocytes. A variety of accessory molecules further modulate T-cell signaling. Of these, the CD4 and CD8 coreceptors make the most critical contributions to T cell sensitivity in vivo. Whereas, CD4 function in T cell development is well-characterized, its role in peripheral T cells remains incompletely understood. It was originally suggested that CD4 stabilizes weak interactions between TCRs and peptides in the MHC and delivers Lck kinases to that complex. The results of numerous experiments support the latter role, indicating that the CD4-Lck complex accelerates TCR-triggered signaling and controls the availability of the kinase for TCR in the absence of the ligand. On the other hand, extremely low affinity of CD4 for MHC rules out its ability to stabilize the receptor-ligand complex. In this review, we summarize the current knowledge on CD4 in T cells, with a special emphasis on the spatio-temporal organization of early signaling events and the relevance for CD4 function. We further highlight the capacity of CD4 to interact with the MHC in the absence of TCR. It drives the adhesion of T cells to the cells that express the MHC. This process is facilitated by the CD4 accumulation in the tips of microvilli on the surface of unstimulated T cells. Based on these observations, we suggest an alternative model of CD4 role in T-cell activation.

• Klíčová slova
• CD4, Lck, T lymphocytes, TCR coreceptor, cell-cell adhesion, microvilli,
• MeSH
• aktivace lymfocytů * MeSH
• CD4-pozitivní T-lymfocyty cytologie   imunologie   MeSH
• CD8-pozitivní T-lymfocyty cytologie   metabolismus   MeSH
• histokompatibilita - antigeny imunologie   MeSH
• lidé MeSH
• receptory antigenů T-buněk imunologie   MeSH
• signální transdukce imunologie   MeSH
• tyrosinkinasa p56(lck), specifická pro lymfocyty imunologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• histokompatibilita - antigeny MeSH
• receptory antigenů T-buněk MeSH
• tyrosinkinasa p56(lck), specifická pro lymfocyty MeSH

BACKGROUND: Super-resolution single molecule localization microscopy (SMLM) is a method for achieving resolution beyond the classical limit in optical microscopes (approx. 200 nm laterally). Yellow fluorescent protein (YFP) has been used for super-resolution single molecule localization microscopy, but less frequently than other fluorescent probes. Working with YFP in SMLM is a challenge because a lower number of photons are emitted per molecule compared with organic dyes, which are more commonly used. Publically available experimental data can facilitate development of new data analysis algorithms. FINDINGS: Four complete, freely available single molecule super-resolution microscopy datasets on YFP-tagged growth factor receptors expressed in a human cell line are presented, including both raw and analyzed data. We report methods for sample preparation, for data acquisition, and for data analysis, as well as examples of the acquired images. We also analyzed the SMLM datasets using a different method: super-resolution optical fluctuation imaging (SOFI). The 2 modes of analysis offer complementary information about the sample. A fifth single molecule super-resolution microscopy dataset acquired with the dye Alexa 532 is included for comparison purposes. CONCLUSIONS: This dataset has potential for extensive reuse. Complete raw data from SMLM experiments have typically not been published. The YFP data exhibit low signal-to-noise ratios, making data analysis a challenge. These datasets will be useful to investigators developing their own algorithms for SMLM, SOFI, and related methods. The data will also be useful for researchers investigating growth factor receptors such as ErbB3.

• MeSH
• algoritmy MeSH
• bakteriální proteiny chemie   MeSH
• fluorescenční barviva chemie   MeSH
• lidé MeSH
• luminescentní proteiny chemie   MeSH
• receptory růstových faktorů chemie   izolace a purifikace   MeSH
• zobrazení jednotlivé molekuly metody   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriální proteiny MeSH
• fluorescenční barviva MeSH
• luminescentní proteiny MeSH
• receptory růstových faktorů MeSH
• yellow fluorescent protein, Bacteria MeSH Prohlížeč

Quantitative approaches for characterizing molecular organization of cell membrane molecules under physiological and pathological conditions profit from recently developed super-resolution imaging techniques. Current tools employ statistical algorithms to determine clusters of molecules based on single-molecule localization microscopy (SMLM) data. These approaches are limited by the ability of SMLM techniques to identify and localize molecules in densely populated areas and experimental conditions of sample preparation and image acquisition. We have developed a robust, model-free, quantitative clustering analysis to determine the distribution of membrane molecules that excels in densely labeled areas and is tolerant to various experimental conditions, i.e. multiple-blinking or high blinking rates. The method is based on a TIRF microscope followed by a super-resolution optical fluctuation imaging (SOFI) analysis. The effectiveness and robustness of the method is validated using simulated and experimental data investigating nanoscale distribution of CD4 glycoprotein mutants in the plasma membrane of T cells.

• MeSH
• algoritmy MeSH
• antigeny CD4 genetika   metabolismus   MeSH
• buněčná membrána metabolismus   MeSH
• fluorescenční barviva MeSH
• fluorescenční mikroskopie metody   statistika a číselné údaje   MeSH
• Jurkat buňky MeSH
• lidé MeSH
• membránové proteiny genetika   metabolismus   MeSH
• mutantní proteiny genetika   metabolismus   MeSH
• optické zobrazování metody   statistika a číselné údaje   MeSH
• shluková analýza MeSH
• T-lymfocyty imunologie   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• validační studie MeSH
• Názvy látek
• antigeny CD4 MeSH
• fluorescenční barviva MeSH
• membránové proteiny MeSH
• mutantní proteiny MeSH

Super-resolution optical fluctuation imaging overcomes the diffraction limit by analyzing fluctuations in the fluorophore emission. A key assumption of the imaging is that the fluorophores are independent, though this is invalidated in the presence of photodestruction. In this work, we evaluate the effect of photodestruction on SOFI imaging using theoretical considerations and computer simulations. We find that photodestruction gives rise to an additional signal that does not present an easily interpretable view of the sample structure. This additional signal is strong and the resulting images typically exhibit less noise. Accordingly, these images may be mis-interpreted as being more visually pleasing or more informative. To address this uncertainty, we develop a procedure that can robustly estimate to what extent any particular experiment is affected by photodestruction. We also develop a detailed assessment methodology and use it to evaluate the performance of several correction algorithms. We identify two approaches that can correct for the presence of even strong photodestruction, one of which can be implemented directly in the SOFI calculation software.

• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH