Application NoteChannel:
Cells:
Tools:

mTRPM7
HEK293Port-a-Patch

TRPM7 activation by internal sequesteringof Mg2+ ions recorded on the Port-a-Patch
Theelectrophysiology

teamatNanion

Technologies

GmbH,Munich.

Cells were kindly provided by V. Chubanov & T. Gudermann, LMU, Munich

Summary

Results

Transient receptor potential (TRP) channels are an

Current responses of a cell induced to express mTRPM7

important class of receptors found widely distributed​

are shown in Figure 1. Currents were elicited using athroughout the mammalian central and peripheral

voltage ramp from -100 mV to +100 mV over 200 ms.

nervousbeWhen Mg2+ ions were sequestered in the internal solution

temperature,using internal EGTA or BAPTA, some run-up of the current

mechano-stimulation, divalent cations and pH, amongst

could be seen at the start of the recording (consistent withsystems.

activatedby

They

many

havestimuli

beenshownincludingtoothers. TRP channels are receiving much attention as

the literature3) and the recording was stable for several

potential targets for the treatment of, for example, pain,minutes. The shape of the ramp, with little inward current

respiratory diseases such as asthma, cancer and immune

but a large outward current is in good agreement withthe literature1,3,7.

BAThe TRPM7 receptor is thought to play a role inmagnesium homeostasis1,2,3. A role for TRPM7 in intra-

cellular pH sensing4, the pathological response to bloodvessel wall injury5 and cell adhesion6 has also beensuggested. In electrophysiological studies TRPM7 canbe recorded using a voltage ramp protocol. It displays
a characteristic large outward current with little inward
current and can be blocked by the presence of internal
Mg2+ ions1,3,7.

Here we present data recorded on the Port-a-Patch withinternal perfusion showing recordings of mouse TRPM7(mTRPM7) and block of this channel by the internal
perfusion of Mg2+ ions.

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00.5 nA
50 ms

Current Amplitude (nA)disorders (for review see ref. 1).

1.0
0.8
0.6
0.4
0.2
0.0

0100 200
Time (s)Figure 1:
The mTRPM7 current could be stably recorded on the Port-a-Patch. Cells
were induced to express the mTRPM7 receptor using ponasterone andwere recorded using a voltage ramp from -100 to +100 mV over 200 ms(A). After a small run-up of the current after whole cell access, the current was stable for almost 5 minutes (B).

Application Note
Figure 2 shows the current response of a cell induced toIn summary, it is possible to record the TRPM7 current

express mTRPM7 and block of this current upon internalon the Port-a-Patch. What is more, using the internal

perfusion of Mg2+ ions.

perfusion system for the Port-a-Patch, TRPM7 currents
could be blocked by internal perfusion of Mg2+ ions. Theease with which the internal solution can be exchangedon the Port-a-Patch provides a distinct advantage overconventional patch clamp set-ups, where the exchangeof the internal solution is somewhat difficult, due to theControl
2 mM MgCl20100 pA
50 ms

Current Amplitude (pA)B

AMgCl2

TRPM7 currents could be activated by sequestering Mg2+250

ions on the inside. In this way, pharmacological agents

200for activation or inhibition of the TRPM7 channel perfused150

either internally or externally could be investigated. This100
50

dimensions of the pipette.

may provide further insight into the physiological and
0100 200 300
Time (s)Figure 2:
The mTRPM7 current could be blocked by internal Mg2+ ions. A mTRPM7
current was recorded using a voltage ramp protocol. After some run-up in
the beginning the recording was stable. Using the internal perfusion systemfrom Nanion, Mg2+ ions could be perfused in the internal solution and thisblocked the current. The arrows shown in the timecourse (B) indicate thetime points at which the traces were taken for Panel A.

pathological roles of TRPM7, as well as the identificationof novel agents for activation and antagonism of theTRPM7 channel.

Cell culture

References
1. Clapham, D., 2003. Nature. 426: 517-524
2. Schlingmann, K.P., Gudermann, T., 2005. J. Physiol.
566.2: 301-308
3. Chubanov et al., 2007. J. Biol. Chem. 282: 7656-7667
4. Kozak et al., 2005. J. Gen. Physiol. 126 (5): 499-514
5. Oancea et al., 2010. Circ. Res. 98 (2): 245-253

Cells were cultured and harvested according to Nanion’s standard cell culture protocol. Cells were grown on
the dishes for 1 - 3 days and then media was exchanged
for media containing 5 μM ponasterone for 24 - 48 hours
to induce mTRPM7 expression (as described in ref. 3).
Electrophysiology

6. Clark et al., 2006. EMBO J. 25: 290-301

Whole cell patch clamp recordings were conducted

7. Mederos y Schnitzler et al., 2008. FASEB J. 22 (5): 1540-

according to Nanion’s standard procedure for the Port-1551

a-Patch. The internal perfusion system was also used.
Currents were elicited every 3 s by 200 ms voltage rampsMethods

from -100 mV to +100 mV. Currents were activated or
blocked using EGTA/BAPTA or Mg2+ ions internally,

Cells

respectively.

HEK293 cells containing an inducible mTRPM7 channel
were used.

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